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Wikipedia

PHP

April 18, 2024

This article is about the scripting language. For other uses, see PHP (disambiguation).

PHP is a general-purpose scripting language geared towards web development.[8] It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995.[9][10] The PHP reference implementation is now produced by the PHP Group.[11] PHP was originally an abbreviation of Personal Home Page,[12][13] but it now stands for the recursive initialism PHP: Hypertext Preprocessor.[14]

PHP
ParadigmMulti-paradigm: imperative, functional, object-oriented, procedural, reflective
Designed byRasmus Lerdorf
DeveloperThe PHP Development Team, Zend Technologies, PHP Foundation
First appeared8 June 1995; 28 years ago (1995-06-08)[1][2]
Stable release
8.3.6 / 11 April 2024; 3 days ago (2024-04-11)[3]
Typing disciplineDynamic, weak, gradual[4]
Implementation languageC (primarily; some components C++)
OSUnix-like, Windows, macOS, IBM i, OpenVMS, IBM Z
Licensedual licensed GNU General Public License version 2 or any later version and PHP License for PHP versions 3.0 or earlier.[5] Only PHP License (most of Zend engine under Zend Engine License) for 3.01x and later versions.
Filename extensions.php,.phar,.phtml,.pht,.phps
Websitewww.php.net
Major implementations
Zend Engine, HHVM, PeachPie, Quercus, Parrot
Influenced by
Perl, C, C++, Java,[6] Tcl,[2] JavaScript[7]
Influenced
Hack, JSP, ASP, React JS
  • PHP Programming at Wikibooks

PHP code is usually processed on a web server by a PHP interpreter implemented as a module, a daemon or a Common Gateway Interface (CGI) executable. On a web server, the result of the interpreted and executed PHP code—which may be any type of data, such as generated HTML or binary image data—would form the whole or part of an HTTP response. Various web template systems, web content management systems, and web frameworks exist that can be employed to orchestrate or facilitate the generation of that response. Additionally, PHP can be used for many programming tasks outside the web context, such as standalone graphical applications[15] and drone control.[16] PHP code can also be directly executed from the command line.

The standard PHP interpreter, powered by the Zend Engine, is free software released under the PHP License. PHP has been widely ported and can be deployed on most web servers on a variety of operating systems and platforms.[17]

The PHP language has evolved without a written formal specification or standard, with the original implementation acting as the de facto standard that other implementations aimed to follow.

W3Techs reports that as of 23 March 2024 (the four months after the PHP 8.3 release), PHP is used by 76.4% of all websites whose programming language could be determined, and 57.2% thereof use PHP 7 which is outdated and known to be insecure.[18] Additionally, PHP 8.0, is no longer supported,[19] meaning the vast majority of PHP users utilize outdated versions, and well over half of all websites, PHP-using or not (whose programming language could be determined) are insecure.

History edit

 
 
 
Rasmus Lerdorf, creator of PHP; and Andi Gutmans and Zeev Suraski, creators of the Zend Engine

Early history edit

PHP development began in 1993[9] when Rasmus Lerdorf wrote several Common Gateway Interface (CGI) programs in C,[20][21] which he used to maintain his personal homepage. He extended them to work with web forms and to communicate with databases, and called this implementation "Personal Home Page/Forms Interpreter" or PHP/FI.

An example of the early PHP syntax:[22]

<!--include /text/header.html--> <!--getenv HTTP_USER_AGENT--> <!--if substr $exec_result Mozilla--> Hey, you are using Netscape!<p> <!--endif--> <!--sql database select * from table where user='$username'--> <!--ifless $numentries 1--> Sorry, that record does not exist<p> <!--endif exit--> Welcome <!--$user-->!<p> You have <!--$index:0--> credits left in your account.<p> <!--include /text/footer.html-->

PHP/FI could be used to build simple, dynamic web applications. To accelerate bug reporting and improve the code, Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" on the Usenet discussion group comp.infosystems.www.authoring.cgi on 8 June 1995.[1][23] This release included basic functionality such as Perl-like variables, form handling, and the ability to embed HTML. By this point, the syntax had changed to resemble that of Perl, but was simpler, more limited, and less consistent.[12][11]

Early PHP was never intended to be a new programming language; rather, it grew organically, with Lerdorf noting in retrospect: "I don't know how to stop it [...] there was never any intent to write a programming language [...] I have absolutely no idea how to write a programming language [...] I just kept adding the next logical step on the way."[24] A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997.[25][citation needed]

The fact that PHP was not originally designed, but instead was developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters.[26] In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping",[27] while in some very early versions of PHP the length of the function names was used internally as a hash function, so names were chosen to improve the distribution of hash values.[28]

PHP 3 and 4 edit

 
This is an example of PHP code for the WordPress content management system.

Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive acronym PHP: Hypertext Preprocessor.[11][29] Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend Engine in 1999.[30] They also founded Zend Technologies in Ramat Gan, Israel.[11]

On 22 May 2000, PHP 4, powered by the Zend Engine 1.0, was released.[11] By August 2008, this branch had reached version 4.4.9. PHP 4 is now no longer under development and nor are any security updates planned to be released.[31][32]

PHP 5 edit

On 1 July 2004, PHP 5 was released, powered by the new Zend Engine II.[11] PHP 5 included new features such as improved support for object-oriented programming, the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements.[33] In 2008, PHP 5 became the only stable version under development. Late static binding had been missing from previous versions of PHP, and was added in version 5.3.[34][35]

Many high-profile open-source projects ceased to support PHP 4 in new code from February 5, 2008, because of the GoPHP5 initiative,[36] provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.[37][38]

Over time, PHP interpreters became available on most existing 32-bit and 64-bit operating systems, either by building them from the PHP source code or by using pre-built binaries.[39] For PHP versions 5.3 and 5.4, the only available Microsoft Windows binary distributions were 32-bit IA-32 builds,[40][41] requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit x86-64 builds available for Microsoft Windows.[42]

Official security support for PHP 5.6 ended on 31 December 2018.[43]

PHP 6 and Unicode edit

PHP received mixed reviews due to lacking native Unicode support at the core language level.[44][45] In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the International Components for Unicode (ICU) library, and representing text strings as UTF-16 internally.[46] Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.[47]

However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project.[48] As a result, a PHP 5.3 release was created in 2009, with many non-Unicode features back-ported from PHP 6, notably namespaces. In March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared to contain most remaining non-Unicode features from PHP 6, such as traits and closure re-binding.[49] Initial hopes were that a new plan would be formed for Unicode integration, but by 2014 none had been adopted.[citation needed]

PHP 7 edit

During 2014 and 2015, a new major PHP version was developed, PHP 7. The numbering of this version involved some debate among internal developers.[50] While the PHP 6 Unicode experiments had never been released, several articles and book titles referenced the PHP 6 names, which might have caused confusion if a new release were to reuse the name.[51] After a vote, the name PHP 7 was chosen.[52]

The foundation of PHP 7 is a PHP branch that was originally dubbed PHP next generation (phpng). It was authored by Dmitry Stogov, Xinchen Hui and Nikita Popov,[53] and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility.[54] By 14 July 2014, WordPress-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng make it easier to improve performance in future versions, as more compact data structures and other changes are seen as better suited for a successful migration to a just-in-time (JIT) compiler.[55] Because of the significant changes, the reworked Zend Engine was called Zend Engine 3, succeeding Zend Engine 2 used in PHP 5.[56]

Because of the major internal changes in phpng, it must receive a new major version number of PHP, rather than a minor PHP 5 release, according to PHP's release process.[57] Major versions of PHP are allowed to break backward-compatibility of code and therefore PHP 7 presented an opportunity for other improvements beyond phpng that require backward-compatibility breaks.[citation needed] In particular, it involved the following changes:

  • Many fatal or recoverable-level legacy PHP error mechanisms were replaced with modern object-oriented exceptions.[58]
  • The syntax for variable dereferencing was reworked to be internally more consistent and complete, allowing the use of the operators ->, [], (),{}, and ::, with arbitrary meaningful left-side expressions.[59]
  • Support for legacy PHP 4-style constructor methods was deprecated.[60]
  • The behavior of the foreach statement was changed to be more predictable.[61]
  • Constructors for the few classes built-in to PHP which returned null upon failure were changed to throw an exception instead, for consistency.[62]
  • Several unmaintained or deprecated server application programming interfaces (SAPIs) and extensions were removed from the PHP core, most notably the legacy mysql extension.[63]
  • The behavior of the list() operator was changed to remove support for strings.[64]
  • Support was removed for legacy ASP-style delimiters <% and %> and <script language="php"> ... </script>.[65]
  • An oversight allowing a switch statement to have multiple default clauses was fixed.[66]
  • Support for hexadecimal number support in some implicit conversions from strings to number types was removed.[67]
  • The left-shift and right-shift operators were changed to behave more consistently across platforms.[68]
  • Conversions between floating-point numbers and integers were changed (e.g. infinity changed to convert to zero) and implemented more consistently across platforms.[68][69]

PHP 7 also included new language features. Most notably, it introduced return type declarations for functions[70] which complement the existing parameter type declarations, and support for the scalar types (integer, float, string, and boolean) in parameter and return type declarations.[71]

PHP 8 edit

PHP 8 was released on 26 November 2020, and is currently the second-most used PHP major version. PHP 8 is a major version and has breaking changes from previous versions.[72][73] New features and notable changes include:

Just-in-time compilation edit

Just-in-time compilation is supported in PHP 8.[74]

PHP 8's JIT compiler can provide substantial performance improvements for some use cases,[75][76] while PHP developer Nikita Popov stated that the performance improvements for most websites will be less substantial than the upgrade from PHP 5 to PHP 7.[77] Substantial improvements are expected more for mathematical-type operations than for common web-development use cases.[77] Additionally, the JIT compiler provides the future potential to move some code from C to PHP, due to the performance improvements for some use cases.[78]

Addition of the match expression edit

Main article: PHP syntax and semantics § Match expression

PHP 8 introduced the match expression.[79] The match expression is conceptually similar to a switch statement and is more compact for some use cases.[80] Because match is an expression, its result can be assigned to a variable or returned from a function.[81]

Type changes and additions edit

PHP 8 introduced union types, a new static return type, and a new mixed type.[72]

"Attributes", often referred to as "annotations" in other programming languages, were added in PHP 8, which allow metadata to be added to classes.[72]

throw was changed from being a statement to being an expression.[82] This allows exceptions to be thrown in places that were not previously possible.[72]

Syntax changes and additions edit

PHP 8 includes changes to allow alternate, more concise, or more consistent syntaxes in a number of scenarios. For example, the nullsafe operator is similar to the null coalescing operator ??, but used when calling methods.[83] The following code snippet will not throw an error if getBirthday() returns null: 

$human_readable_date = $user->getBirthday()?->diffForHumans();

Constructor property promotion has been added as "syntactic sugar," allowing class properties to be set automatically when parameters are passed into a class constructor.[72] This reduces the amount of boilerplate code that must be written.[citation needed]

Other minor changes include support for use of ::class on objects, which serves as an alternative for the use of get_class();[72] non-capturing catches in try-catch blocks; variable syntax tweaks to resolve inconsistencies; support for named arguments; and support for trailing commas in parameter lists, which adds consistency with support for trailing commas in other contexts, such as in arrays.[citation needed]

Standard library changes and additions edit

  • Weak maps were added in PHP 8. A WeakMap holds references to objects, but these references do not prevent such objects from being garbage collected.[84] This can provide performance improvements in scenarios where data is being cached; this is of particular relevance for object–relational mappings (ORM).[72]
  • Various adjustments to interfaces, such as adding support for creating DateTime objects from interfaces, and the addition of a Stringable interface that can be used for type hinting.[citation needed]
  • Various new functions including str_contains(), str_starts_with(), and str_ends_with();[85] fdiv(); get_debug_type(); and get_resource_id()[citation needed]
  • Object implementation of token_get_all()[citation needed]

Additional changes edit

  • Type annotations were also added into PHP's C source code itself to allow internal functions and methods to have "complete type information in reflection."[86]
  • Inheritance with private methods[citation needed]
  • Abstract methods in traits improvements[citation needed]

PHP 8.1 edit

PHP 8.1 was released on November 25, 2021.[87] It added support for enumerations (also called "enums"), declaring properties as readonly (which prevents modification of the property after initialization), and array unpacking with string keys. The new never type can be used to indicate that a function does not return.[88]

PHP 8.2 edit

PHP 8.2 was released on December 8, 2022.[89] New in this release are readonly classes (whose instance properties are implicitly readonly), disjunctive normal form (DNF) types, and the random extension, which provides a pseudorandom number generator with an object-oriented API.[90]

Release history edit

Version Release date Supported until[91] Notes
Old version, no longer maintained: 1.0 8 June 1995 Officially called "Personal Home Page Tools (PHP Tools)". This is the first use of the name "PHP".[11]
Old version, no longer maintained: 2.0 1 November 1997 Officially called "PHP/FI 2.0". This is the first release that could actually be characterised as PHP, being a standalone language with many features that have endured to the present day.
Old version, no longer maintained: 3.0 6 June 1998 20 October 2000[91] Development moves from one person to multiple developers. Zeev Suraski and Andi Gutmans rewritten the base for this version.[11]
Old version, no longer maintained: 4.0 22 May 2000[92] 23 June 2001[91] Added more advanced two-stage parse/execute tag-parsing system called the Zend engine.[93]
Old version, no longer maintained: 4.1 10 December 2001[94] 12 March 2002[91] Introduced "superglobals" ($_GET, $_POST, $_SESSION, etc.)[93]
Old version, no longer maintained: 4.2 22 April 2002[95] 6 September 2002[91] Disabled register_globals by default. Data received over the network is not inserted directly into the global namespace anymore, closing possible security holes in applications.[93]
Old version, no longer maintained: 4.3 27 December 2002[96] 31 March 2005[91] Introduced the command-line interface (CLI), to supplement the CGI.[93][97]
Old version, no longer maintained: 4.4 11 July 2005[98] 7 August 2008[91] Fixed a memory corruption bug, which required breaking binary compatibility with extensions compiled against PHP version 4.3.x.[99]
Old version, no longer maintained: 5.0 13 July 2004[100] 5 September 2005[91] Zend Engine II with a new object model.[101]
Old version, no longer maintained: 5.1 24 November 2005[102] 24 August 2006[91] Performance improvements with the introduction of compiler variables in re-engineered PHP Engine.[101] Added PHP Data Objects (PDO) as a consistent interface for accessing databases.[103]
Old version, no longer maintained: 5.2 2 November 2006[104] 6 January 2011[91] Enabled the filter extension by default. Native JSON support.[101]
Old version, no longer maintained: 5.3 30 June 2009[105] 14 August 2014[91] Namespace support; late static bindings, jump label (limited goto), anonymous functions, closures, PHP archives (phar), garbage collection for circular references, improved Windows support, sqlite3, mysqlnd as a replacement for libmysql as the underlying library for the extensions that work with MySQL, fileinfo as a replacement for mime_magic for better MIME support, the Internationalization extension, and deprecation of ereg extension.
Old version, no longer maintained: 5.4 1 March 2012[106] 3 September 2015[91] Trait support, short array syntax support. Removed items: register_globals, safe_mode, allow_call_time_pass_reference, session_register(), session_unregister() and session_is_registered(). Built-in web server.[107] Several improvements to existing features, performance and reduced memory requirements.
Old version, no longer maintained: 5.5 20 June 2013[108] 10 July 2016[109] Support for generators, finally blocks for exceptions handling, OpCache (based on Zend Optimizer+) bundled in official distribution.[110]
Old version, no longer maintained: 5.6 28 August 2014[111] 31 December 2018[109] Constant scalar expressions, variadic functions, argument unpacking, new exponentiation operator, extensions of the use statement for functions and constants, new phpdbg debugger as a SAPI module, and other smaller improvements.[112]
6.x Not released — Abandoned version of PHP that planned to include native Unicode support.[113][114]
Old version, no longer maintained: 7.0 3 December 2015[115] 10 January 2019[57] Zend Engine 3 (performance improvements[55] and 64-bit integer support on Windows[116]), uniform variable syntax,[59] AST-based compilation process,[117] added Closure::call(),[118] bitwise shift consistency across platforms,[119] ?? (null coalesce) operator,[120] Unicode code point escape syntax,[121] return type declarations,[70] scalar type (integer, float, string and boolean) declarations,[71] <=> "spaceship" three-way comparison operator,[122] generator delegation,[123] anonymous classes,[124] simpler and more consistently available CSPRNG API,[125] replacement of many remaining internal PHP "errors" with the more modern exceptions,[58] and shorthand syntax for importing multiple items from a namespace.[126]
Old version, no longer maintained: 7.1 1 December 2016 1 December 2019[109] iterable type,[127] nullable types,[128] void return type,[129] class constant visibility modifiers,[130] short list syntax,[131] multi-catch[132]
Old version, no longer maintained: 7.2 30 November 2017 30 November 2020[109] Object parameter and return type declaration,[133] libsodium extension,[134] abstract method overriding,[135] parameter type widening[136]
Old version, no longer maintained: 7.3 6 December 2018[137] 6 December 2021 Flexible Heredoc and Nowdoc syntax,[138] support for reference assignment and array deconstruction with list(),[139] PCRE2 support,[140] hrtime function[141]
Old version, no longer maintained: 7.4 28 November 2019[142] 28 November 2022 Typed properties 2.0,[143] preloading,[144] null-coalescing assignment operator,[145] improve openssl_random_pseudo_bytes,[146] weak references,[84] foreign function interface (FFI),[147] always available hash extension,[148] password hash registry,[149] multibyte string splitting,[150] reflection for references,[151] unbundle ext/wddx,[152] new custom object serialization mechanism[153]
Old version, no longer maintained: 8.0 26 November 2020[154] 26 November 2023 Just-In-Time (JIT) compilation,[74] arrays starting with a negative index,[155] stricter/saner language semantics (validation for abstract trait methods),[156] saner string to number comparisons,[157] saner numeric strings,[158] TypeError on invalid arithmetic/bitwise operators,[159] reclassification of various engine errors,[160] consistent type errors for internal functions,[161] fatal error for incompatible method signatures[162]), locale-independent float to string conversion,[163] variable syntax tweaks,[164] attributes,[165][166][167][168] named arguments,[169] match expression,[170] constructor property promotion,[171] union types,[172] mixed type,[173] static return type,[174] nullsafe operator,[83] non-capturing catches,[175] throw expression,[82] JSON extension is always available.[176]
Older version, yet still maintained: 8.1 25 November 2021[177] 25 November 2024 Explicit octal integer literal notation,[178] enumerations,[179] read-only properties,[180] first-class callable syntax,[181] new in initializers,[182] pure intersection types,[183] never return type,[184] final class constraints,[185] fibers[186]
Older version, yet still maintained: 8.2 8 December 2022[187] 8 December 2025 Readonly classes,[188] null, false, and true as stand-alone types,[189][190] locale-independent case conversion,[191] disjunctive normal form types,[192] constants in traits[193]
Current stable version: 8.3 23 November 2023[194] 23 November 2026 Typed class constants,[195] dynamic class constant fetch,[196] #[\Override] attribute,[197] deep-cloning of read-only properties,[198] new json_validate function,[199] randomizer additions,[200] the command-line linter supports multiple files
Future release: 8.4 21 November 2024[201] 21 November 2027
Legend:
Old version
Older version, still maintained
Latest version
Latest preview version
Future release

Beginning on 28 June 2011, the PHP Development Team implemented a timeline for the release of new versions of PHP.[57] Under this system, at least one release should occur every month. Once per year, a minor release should occur which may include new features. Every minor release should at least be supported for two years with security and bug fixes, followed by at least one year of only security fixes, for a total of a three-year release process for every minor release. No new features, unless small and self-contained, are to be introduced into a minor release during the three-year release process.

Mascot edit

 
The elePHPant, PHP mascot

The mascot of the PHP project is the elePHPant, a blue elephant with the PHP logo on its side, designed by Vincent Pontier[202] in 1998.[203] "The (PHP) letters were forming the shape of an elephant if viewed in a sideways angle."[204] The elePHPant is sometimes differently coloured when in plush toy form.[205]

Many variations of this mascot have been made over the years. Only the elePHPants based on the original design by Vincent Pontier are considered official by the community.[206] These are collectable and some of them are extremely rare.[207]

Syntax edit

Main article: PHP syntax and semantics
 
A "Hello World" application in PHP 7.4 running on its built-in development server

The following "Hello, World!" program is written in PHP code embedded in an HTML document: 

<!DOCTYPE html> <html> <head> <title>PHP "Hello, World!" program</title> </head> <body>  <p><?= 'Hello, World!' ?></p>  </body> </html>

However, as no requirement exists for PHP code to be embedded in HTML, the simplest version of Hello, World! may be written like this, with the closing tag ?> omitted as preferred in files containing pure PHP code.[208]

<?php echo 'Hello, World!';

The PHP interpreter only executes PHP code within its delimiters. Anything outside of its delimiters is not processed by PHP, although the non-PHP text is still subject to control structures described in PHP code. The most common delimiters are <?php to open and ?> to close PHP sections. The shortened form <? also exists. This short delimiter makes script files less portable since support for them can be disabled in the local PHP configuration and it is therefore discouraged.[209][210] Conversely, there is no recommendation against the echo short tag <?=.[211] Prior to PHP 5.4.0, this short syntax for echo only works with the short_open_tag configuration setting enabled, while for PHP 5.4.0 and later it is always available.[212][213][209] The purpose of all these delimiters is to separate PHP code from non-PHP content, such as JavaScript code or HTML markup.[214] So the shortest "Hello, World!" program written in PHP is: 

<?='Hello, World!';

The first form of delimiters, <?php and ?>, in XHTML and other XML documents, creates correctly formed XML processing instructions.[215] This means that the resulting mixture of PHP code and other markups in the server-side file is itself well-formed XML.

Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. PHP 5 introduced type declarations that allow functions to force their parameters to be objects of a specific class, arrays, interfaces or callback functions. However, before PHP 7, type declarations could not be used with scalar types such as integers or strings.[71]

Below is an example of how PHP variables are declared and initialized. 

<?php $name = 'John'; // variable of string type being declared and initialized $age = 18; // variable of integer type being declared and initialized $height = 5.3; // variable of double type being declared and initialized echo $name . ' is ' . $height . "m tall\n"; // concatenating variables and strings echo "$name is $age years old."; // interpolating variables to string ?>

Unlike function and class names, variable names are case-sensitive. Both double-quoted ("") and heredoc strings provide the ability to interpolate a variable's value into the string.[216] PHP treats newlines as whitespace in the manner of a free-form language, and statements are terminated by a semicolon.[217] PHP has three types of comment syntax: /* */ marks block and inline comments; // or # are used for one-line comments.[218] The echo statement is one of several facilities PHP provides to output text.[citation needed]

In terms of keywords and language syntax, PHP is similar to C-style syntax. if conditions, for and while loops and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.[citation needed]

Data types edit

PHP is loosely typed. It stores integers in a platform-dependent range, either as a 32, 64 or 128-bit signed integer equivalent to the C-language long type. Unsigned integers are converted to signed values in certain situations, which is different behaviour to many other programming languages.[219] Integer variables can be assigned using decimal (positive and negative), octal, hexadecimal, and binary notations.[citation needed]

Floating-point numbers are also stored in a platform-specific range. They can be specified using floating-point notation, or two forms of scientific notation.[220] PHP has a native Boolean type that is similar to the native Boolean types in Java and C++. Using the Boolean type conversion rules, non-zero values are interpreted as true and zero as false, as in Perl and C++.[220]

The null data type represents a variable that has no value; NULL is the only allowed value for this data type.[220]

Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by functions from the same extension; examples include file, image, and database resources.[220]

Arrays can contain elements of any type that PHP can handle, including resources, objects, and even other arrays. Order is preserved in lists of values and in hashes with both keys and values, and the two can be intermingled.[220] PHP also supports strings, which can be used with single quotes, double quotes, nowdoc or heredoc syntax.[221]

The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.[222]

Functions edit

PHP defines a large array of functions in the core language and many are also available in various extensions; these functions are well documented online PHP documentation.[223] However, the built-in library has a wide variety of naming conventions and associated inconsistencies, as described under history above.

Custom functions may be defined by the developer: 

function myAge(int $birthYear): string { // calculate the age by subtracting the birth year from the current year. $yearsOld = date('Y') - $birthYear; // return the age in a descriptive string. return $yearsOld . ($yearsOld == 1 ? ' year' : ' years'); } echo 'I am currently ' . myAge(1995) . ' old.';

As of 2024, the output of the above sample program is "I am currently 29 years old."

In lieu of function pointers, functions in PHP can be referenced by a string containing their name. In this manner, normal PHP functions can be used, for example, as callbacks or within function tables.[224] User-defined functions may be created at any time without being prototyped.[223][224] Functions may be defined inside code blocks, permitting a run-time decision as to whether or not a function should be defined. There is a function_exists function that determines whether a function with a given name has already been defined. Function calls must use parentheses, with the exception of zero-argument class constructor functions called with the PHP operator new, in which case parentheses are optional.[citation needed]

Since PHP 4.0.1 create_function(), a thin wrapper around eval(), allowed normal PHP functions to be created during program execution; it was deprecated in PHP 7.2 and removed in PHP 8.0[225] in favor of syntax for anonymous functions or "closures"[226] that can capture variables from the surrounding scope, which was added in PHP 5.3. Shorthand arrow syntax was added in PHP 7.4:[227]

function getAdder($x) { return fn($y) => $x + $y; } $adder = getAdder(8); echo $adder(2); // prints "10"

In the example above, getAdder() function creates a closure using passed argument $x, which takes an additional argument $y, and returns the created closure to the caller. Such a function is a first-class object, meaning that it can be stored in a variable, passed as a parameter to other functions, etc.[228]

Unusually for a dynamically typed language, PHP supports type declarations on function parameters, which are enforced at runtime. This has been supported for classes and interfaces since PHP 5.0, for arrays since PHP 5.1, for "callables" since PHP 5.4, and scalar (integer, float, string and boolean) types since PHP 7.0.[71] PHP 7.0 also has type declarations for function return types, expressed by placing the type name after the list of parameters, preceded by a colon.[70] For example, the getAdder function from the earlier example could be annotated with types like so in PHP 7: 

function getAdder(int $x): Closure { return fn(int $y): int => $x + $y; } $adder = getAdder(8); echo $adder(2); // prints "10" echo $adder(null); // throws an exception because an incorrect type was passed $adder = getAdder([]); // would also throw an exception

By default, scalar type declarations follow weak typing principles. So, for example, if a parameter's type is int, PHP would allow not only integers, but also convertible numeric strings, floats or booleans to be passed to that function, and would convert them.[71] However, PHP 7 has a "strict typing" mode which, when used, disallows such conversions for function calls and returns within a file.[71]

PHP objects edit

Basic object-oriented programming functionality was added in PHP 3 and improved in PHP 4.[11] This allowed for PHP to gain further abstraction, making creative tasks easier for programmers using the language. Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance.[229] In previous versions of PHP, objects were handled like value types.[229] The drawback of this method was that code had to make heavy use of PHP's "reference" variables if it wanted to modify an object it was passed rather than creating a copy of it. In the new approach, objects are referenced by handle, and not by value.[citation needed]

PHP 5 introduced private and protected member variables and methods, along with abstract classes, final classes, abstract methods, and final methods. It also introduced a standard way of declaring constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception handling model. Furthermore, PHP 5 added interfaces and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach language construct. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference at compile time.[230]

If the developer creates a copy of an object using the reserved word clone, the Zend engine will check whether a __clone() method has been defined. If not, it will call a default __clone() which will copy the object's properties. If a __clone() method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so the programmer can start with a by-value replica of the source object and only override properties that need to be changed.[231]

The visibility of PHP properties and methods is defined using the keywords public, private, and protected. The default is public, if only var is used; var is a synonym for public. Items declared public can be accessed everywhere. protected limits access to inherited classes (and to the class that defines the item). private limits visibility only to the class that defines the item.[232] Objects of the same type have access to each other's private and protected members even though they are not the same instance.[citation needed]

Example edit

The following is a basic example of object-oriented programming in PHP 8: 

<?php  abstract class User {  protected string $name;   public function __construct(string $name)  {  // make first letter uppercase and the rest lowercase  $this->name = ucfirst(strtolower($name));  }   public function greet(): string  {  return "Hello, my name is " . $this->name;  }   abstract public function job(): string; }  class Student extends User {  public function __construct(string $name, private string $course)  {  parent::__construct($name);  }   public function job(): string  {  return "I learn " . $this->course;  } }  class Teacher extends User {  public function __construct(string $name, private array $teachingCourses)  {  parent::__construct($name);  }   public function job(): string  {  return "I teach " . implode(", ", $this->teachingCourses);  } }  $students = [  new Student("Alice", "Computer Science"),  new Student("Bob", "Computer Science"),  new Student("Charlie", "Business Studies"), ];  $teachers = [  new Teacher("Dan", ["Computer Science", "Information Security"]),  new Teacher("Erin", ["Computer Science", "3D Graphics Programming"]),  new Teacher("Frankie", ["Online Marketing", "Business Studies", "E-commerce"]), ];  foreach ([$students, $teachers] as $users) {  echo $users[0]::class . "s:\n";   array_walk($users, function (User $user) {  echo "{$user->greet()}, {$user->job()}\n";  }); }

This program outputs the following: 

Students: Hello, my name is Alice, I learn Computer Science Hello, my name is Bob, I learn Computer Science Hello, my name is Charlie, I learn Business Studies Teachers: Hello, my name is Dan, I teach Computer Science, Information Security Hello, my name is Erin, I teach Computer Science, 3D Graphics Programming Hello, my name is Frankie, I teach Online Marketing, Business Studies, E-commerce

Implementations edit

The only complete PHP implementation is the original, known simply as PHP. It is the most widely used and is powered by the Zend Engine. To disambiguate it from other implementations, it is sometimes unofficially called "Zend PHP". The Zend Engine compiles PHP source code on-the-fly into an internal format that it can execute, thus it works as an interpreter.[233][234] It is also the "reference implementation" of PHP, as PHP has no formal specification, and so the semantics of Zend PHP define the semantics of PHP. Due to the complex and nuanced semantics of PHP, defined by how Zend works, it is difficult for competing implementations to offer complete compatibility.[citation needed]

PHP's single-request-per-script-execution model, and the fact that the Zend Engine is an interpreter, leads to inefficiency; as a result, various products have been developed to help improve PHP performance. In order to speed up execution time and not have to compile the PHP source code every time the web page is accessed, PHP scripts can also be deployed in the PHP engine's internal format by using an opcode cache, which works by caching the compiled form of a PHP script (opcodes) in shared memory to avoid the overhead of parsing and compiling the code every time the script runs. An opcode cache, Zend Opcache, is built into PHP since version 5.5.[235] Another example of a widely used opcode cache is the Alternative PHP Cache (APC), which is available as a PECL extension.[236]

While Zend PHP is still the most popular implementation, several other implementations have been developed. Some of these are compilers or support JIT compilation, and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility.[citation needed] Alternative implementations include the following:

  • HHVM (HipHop Virtual Machine) – developed at Facebook and available as open source, it converts PHP code into a high-level bytecode (commonly known as an intermediate language), which is then translated into x86-64 machine code dynamically at runtime by a just-in-time (JIT) compiler, resulting in up to 6× performance improvements.[237] However, since version 7.2 Zend has outperformed HHVM,[238] and HHVM 3.24 is the last version to officially support PHP.[239]
    • HipHop – developed at Facebook and available as open source, it transforms the PHP scripts into C++ code and then compiles the resulting code, reducing the server load up to 50%. In early 2013, Facebook deprecated it in favour of HHVM due to multiple reasons, including deployment difficulties and lack of support for the whole PHP language, including the create_function() and eval() constructs.[240]
  • Parrot – a virtual machine designed to run dynamic languages efficiently; the cross-translator Pipp transforms the PHP source code into the Parrot intermediate representation, which is then translated into the Parrot's bytecode and executed by the virtual machine.
  • PeachPie – a second-generation compiler to .NET Common Intermediate Language (CIL) bytecode, built on the Roslyn platform; successor of Phalanger, sharing several architectural components
  • Phalanger – compiles PHP into .Net Common Intermediate Language bytecode; predecessor of PeachPie
  • Quercus – compiles PHP into Java bytecode

Licensing edit

Main article: PHP License

PHP is free software released under the PHP License, which stipulates that:[241]

Products derived from this software may not be called "PHP", nor may "PHP" appear in their name, without prior written permission from group@php.net. You may indicate that your software works in conjunction with PHP by saying "Foo for PHP" instead of calling it "PHP Foo" or "phpfoo".

This restriction on the use of "PHP" makes the PHP License incompatible with the General Public License (GPL), while the Zend License is incompatible due to an advertising clause similar to that of the original BSD license.[242]

Development and community edit

PHP includes various free and open-source libraries in its source distribution or uses them in resulting PHP binary builds. PHP is fundamentally an Internet-aware system with built-in modules for accessing File Transfer Protocol (FTP) servers and many database servers, including PostgreSQL, MySQL, Microsoft SQL Server and SQLite (which is an embedded database), LDAP servers, and others. Numerous functions are familiar to C programmers, such as those in the stdio family, are available in standard PHP builds.[243]

PHP allows developers to write extensions in C to add functionality to the PHP language. PHP extensions can be compiled statically into PHP or loaded dynamically at runtime. Numerous extensions have been written to add support for the Windows API, process management on Unix-like operating systems, multibyte strings (Unicode), cURL, and several popular compression formats. Other PHP features made available through extensions include integration with Internet Relay Chat (IRC), dynamic generation of images and Adobe Flash content, PHP Data Objects (PDO) as an abstraction layer used for accessing databases,[244][245][246][247][248][249][250] and even speech synthesis. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions.[251] The PHP Extension Community Library (PECL) project is a repository for extensions to the PHP language.[252]

Some other projects, such as Zephir, provide the ability for PHP extensions to be created in a high-level language and compiled into native PHP extensions. Such an approach, instead of writing PHP extensions directly in C, simplifies the development of extensions and reduces the time required for programming and testing.[253]

By December 2018 the PHP Group consisted of ten people: Thies C. Arntzen, Stig Bakken, Shane Caraveo, Andi Gutmans, Rasmus Lerdorf, Sam Ruby, Sascha Schumann, Zeev Suraski, Jim Winstead, and Andrei Zmievski.[254]

Zend Technologies provides a PHP Certification based on PHP 7[255] exam (and previously based on PHP 5.5) for programmers to become certified PHP developers.

The PHP Foundation edit

PHP
 
FormationNovember 22, 2021; 2 years ago (2021-11-22)
FounderAutomattic, Laravel, Acquia, Zend, Private Packagist, Symfony, Craft CMS, Tideways, PrestaShop, JetBrains[256]
Websitehttps://thephp.foundation

On 26 November 2021, the JetBrains blog announced the creation of The PHP Foundation, which will sponsor the design and development of PHP.[257]

Year Commits Reviews RFCs
2022[258] 683 283 8
2023[259] 784 702 17

The foundation hires "Core Developers" to work on the PHP language's core repository. Roman Pronskiy, a member of the foundation's board, said that they aim to pay "market salaries" to developers.[260]

The response to the foundation has mostly been positive, with the foundation being praised for better supporting the language and helping to stop the decrease in the language's popularity.[261][262] However, it has also been criticised for adding breaking changes to minor versions of PHP, such as in PHP 8.2 where initialising members of a class out-with the original class scope would cause depreciation errors,[263] these changes impacted a number of open source projects including WordPress. [264]

Installation and configuration edit

 
Example output of the phpinfo() function in PHP 7.1

There are two primary ways for adding support for PHP to a web server – as a native web server module, or as a CGI executable. PHP has a direct module interface called server application programming interface (SAPI), which is supported by many web servers including Apache HTTP Server, Microsoft IIS and iPlanet Web Server. Some other web servers, such as OmniHTTPd, support the Internet Server Application Programming Interface (ISAPI), which is Microsoft's web server module interface. If PHP has no module support for a web server, it can always be used as a Common Gateway Interface (CGI) or FastCGI processor; in that case, the web server is configured to use PHP's CGI executable to process all requests to PHP files.[265]

PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the official PHP distribution since version 5.3.3.[266] When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers.[267]

When using PHP for command-line scripting, a PHP command-line interface (CLI) executable is needed. PHP supports a CLI server application programming interface (SAPI) since PHP 4.3.0.[268] The main focus of this SAPI is developing shell applications using PHP. There are quite a few differences between the CLI SAPI and other SAPIs, although they do share many of the same behaviours.[269]

PHP has a direct module interface called SAPI for different web servers;[270] in case of PHP 5 and Apache 2.0 on Windows, it is provided in form of a DLL file called php5apache2.dll,[271] which is a module that, among other functions, provides an interface between PHP and the web server, implemented in a form that the server understands. This form is what is known as a SAPI.[citation needed]

There are different kinds of SAPIs for various web server extensions. For example, in addition to those listed above, other SAPIs for the PHP language include the Common Gateway Interface and command-line interface.[270][272]

PHP can also be used for writing desktop graphical user interface (GUI) applications, by using the PHP-GTK extension. PHP-GTK is not included in the official PHP distribution,[265] and as an extension, it can be used only with PHP versions 5.1.0 and newer. The most common way of installing PHP-GTK is by compiling it from the source code.[273]

When PHP is installed and used in cloud environments, software development kits (SDKs) are provided for using cloud-specific features.[citation needed] For example:

Numerous configuration options are supported, affecting both core PHP features and extensions.[276][277] Configuration file php.ini is searched for in different locations, depending on the way PHP is used.[278] The configuration file is split into various sections,[279] while some of the configuration options can be also set within the web server configuration.[280]

Use edit

 
A broad overview of the LAMP software bundle, displayed here together with Squid

PHP is a general-purpose scripting language that is especially suited to server-side web development, in which case PHP generally runs on a web server. Any PHP code in a requested file is executed by the PHP runtime, usually to create dynamic web page content or dynamic images used on websites or elsewhere.[281] It can also be used for command-line scripting and client-side graphical user interface (GUI) applications. PHP can be deployed on most web servers, many operating systems and platforms, and can be used with many relational database management systems (RDBMS). Most web hosting providers support PHP for use by their clients. It is available free of charge, and the PHP Group provides the complete source code for users to build, customize and extend for their own use.[17]

 
Dynamic web page: example of server-side scripting (PHP and MySQL)

Originally designed to create dynamic web pages, PHP now focuses mainly on server-side scripting,[282] and it is similar to other server-side scripting languages that provide dynamic content from a web server to a client, such as Python, Microsoft's ASP.NET, Sun Microsystems' JavaServer Pages,[283] and mod_perl. PHP has also attracted the development of many software frameworks that provide building blocks and a design structure to promote rapid application development (RAD).[citation needed] Some of these include PRADO, CakePHP, Symfony, CodeIgniter, Laravel, Yii Framework, Phalcon and Laminas, offering features similar to other web frameworks.

The LAMP architecture has become popular in the web industry as a way of deploying web applications.[284] PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL, although the P may also refer to Python, Perl, or some mix of the three. Similar packages, WAMP and MAMP, are also available for Windows and macOS, with the first letter standing for the respective operating system. Although both PHP and Apache are provided as part of the macOS base install, users of these packages seek a simpler installation mechanism that can be more easily kept up to date.[citation needed]

For specific and more advanced usage scenarios, PHP offers a well-defined and documented way for writing custom extensions in C or C++.[285][286][287][288][289][290][291][non-primary source needed] Besides extending the language itself in form of additional libraries, extensions are providing a way for improving execution speed where it is critical and there is room for improvements by using a true compiled language.[292][293] PHP also offers well-defined ways for embedding itself into other software projects. That way PHP can be easily used as an internal scripting language for another project, also providing tight interfacing with the project's specific internal data structures.[294]

PHP received mixed reviews due to lacking support for multithreading at the core language level,[295] though using threads is made possible by the "pthreads" PECL extension.[296][297]

A command line interface, php-cli, and two ActiveX Windows Script Host scripting engines for PHP have been produced.[citation needed]

Popularity and usage statistics edit

Usage share of PHP versions on 23 March 2024:
four months after PHP 8.3's release[18][298][299][300][301]

  PHP 8.3: 2.10% of PHP 8 (0.56%)
  PHP 8.2: 18.3% of PHP 8 (4.85%)
  PHP 8.1: 40.7% of PHP 8 (10.79%)
  PHP 8.0: 38.9% of PHP 8 (10.31%)
  PHP 7.4: 69.0% of PHP 7 (39.47%)
  PHP 7.3: 13.2% of PHP 7 (7.55%)
  PHP 7.2: 9.60% of PHP 7 (5.49%)
  PHP 7.1: 3.90% of PHP 7 (2.23%)
  PHP 7.0: 4.30% of PHP 7 (2.46%)
  PHP 5.6: 54.0% of PHP 5 (8.7480%)
  PHP 5.5: 8.40% of PHP 5 (1.3608%)
  PHP 5.4: 15.4% of PHP 5 (2.4948%)
  PHP 5.3: 14.9% of PHP 5 (2.4138%)
  PHP 5.2: 6.80% of PHP 5 (1.1016%)
  PHP 5.1: 0.40% of PHP 5 (0.0648%)
  PHP 5.0: 0.10% of PHP 5 (0.0162%)
  PHP 4.4: 78.7% of PHP 4 (0.1574%)
  PHP 4.3: 18.5% of PHP 4 (0.0370%)
  PHP 4.2: 1.60% of PHP 4 (0.0032%)
  PHP 4.1: 0.80% of PHP 4 (0.0016%)
  PHP 4.0: 0.30% of PHP 4 (0.0006%)

PHP is used for Web content management systems including MediaWiki,[302] WordPress,[303] Joomla,[304] Drupal,[305] Moodle,[306] eZ Publish, eZ Platform, and SilverStripe.[307]

As of January 2013, PHP was used in more than 240 million websites (39% of those sampled) and was installed on 2.1 million web servers.[308]

As of 23 March 2024 (four months after PHP 8.3's release), PHP is used as the server-side programming language on 76.4% of websites where the language could be determined; PHP 7 is the most used version of the language with 57.2% of websites using PHP being on that version, while 26.6% use PHP 8, 16.2% use PHP 5 and 0.2% use PHP 4.[18]

Security edit

In 2019, 11% of all vulnerabilities listed by the National Vulnerability Database were linked to PHP;[309] historically, about 30% of all vulnerabilities listed since 1996 in this database are linked to PHP. Technical security flaws of the language itself or of its core libraries are not frequent (22 in 2009, about 1% of the total although PHP applies to about 20% of programs listed).[310] Recognizing that programmers make mistakes, some languages include taint checking to automatically detect the lack of input validation which induces many issues. Such a feature is being developed for PHP,[311] but its inclusion into a release has been rejected several times in the past.[312][313]

There are advanced protection patches such as Suhosin and Hardening-Patch, specially designed for web hosting environments.[314]

Historically, old versions of PHP had some configuration parameters and default values for such runtime settings that made some PHP applications prone to security issues. Among these, magic_quotes_gpc and register_globals[315] configuration directives were the best known; the latter made any URL parameters become PHP variables, opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script. Support for "magic quotes" and "register globals" settings has been deprecated since PHP 5.3.0, and removed from PHP 5.4.0.[316]

Another example for the potential runtime-settings vulnerability comes from failing to disable PHP execution (for example by using the engine configuration directive)[317] for the directory where uploaded files are stored; enabling it can result in the execution of malicious code embedded within the uploaded files.[318][319][320] The best practice is to either locate the image directory outside of the document root available to the web server and serve it via an intermediary script or disable PHP execution for the directory which stores the uploaded files.[citation needed]

Also, enabling the dynamic loading of PHP extensions (via enable_dl configuration directive)[321] in a shared web hosting environment can lead to security issues.[322][323]

Implied type conversions that result in different values being treated as equal, sometimes against the programmer's intent, can lead to security issues. For example, the result of the comparison '0e1234' == '0' is true, because strings that are parsable as numbers are converted to numbers; in this case, the first compared value is treated as scientific notation having the value (0×101234), which is zero. Errors like this resulted in authentication vulnerabilities in Simple Machines Forum,[324] Typo3[325] and phpBB[326] when MD5 password hashes were compared. The recommended way is to use hash_equals() (for timing attack safety), strcmp or the identity operator (===), as '0e1234' === '0' results in false.[327]

In a 2013 analysis of over 170,000 website defacements, published by Zone-H, the most frequently (53%) used technique was the exploitation of file inclusion vulnerability, mostly related to insecure usage of the PHP language constructs include, require, and allow_url_fopen.[328][329]

As of 23 March 2024, (4 months after PHP 8.3 release) W3Techs reports that 83.9% of websites using PHP, use versions 8.0 or older (which are no longer supported by The PHP Development Team).[330] PHP Version 5 is still used by 16.2% of all websites.[299] It is highly recommended to migrate to PHP 8.1 or later and use random_int()[331] instead of rand()[332] or mt_rand(),[333] as the latter functions are not cryptographically secure. There are two attacks that can be performed over PHP entropy sources: "seed attack" and "state recovery attack".[citation needed] With current[when?] GPU technologies, an attacker can perform up to 230 MD5 calculations per second with a $250 GPU, while with an additional $500 can reach up to 232 calculations.[334] In combination with a "birthday attack" this can lead to serious security vulnerabilities.[citation needed]

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Further reading edit

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  • Ford, Paul (June 11, 2015). "What is Code?". Bloomberg Businessweek. What's the Absolute Minimum I Must Know About PHP?

External links edit

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This article is about the scripting language For other uses see PHP disambiguation PHP is a general purpose scripting language geared towards web development 8 It was originally created by Danish Canadian programmer Rasmus Lerdorf in 1993 and released in 1995 9 10 The PHP reference implementation is now produced by the PHP Group 11 PHP was originally an abbreviation of Personal Home Page 12 13 but it now stands for the recursive initialism PHP Hypertext Preprocessor 14 PHPParadigmMulti paradigm imperative functional object oriented procedural reflectiveDesigned byRasmus LerdorfDeveloperThe PHP Development Team Zend Technologies PHP FoundationFirst appeared8 June 1995 28 years ago 1995 06 08 1 2 Stable release8 3 6 11 April 2024 3 days ago 2024 04 11 3 Typing disciplineDynamic weak gradual 4 Implementation languageC primarily some components C OSUnix like Windows macOS IBM i OpenVMS IBM ZLicensedual licensed GNU General Public License version 2 or any later version and PHP License for PHP versions 3 0 or earlier 5 Only PHP License most of Zend engine under Zend Engine License for 3 01x and later versions Filename extensions php phar phtml pht phpsWebsitewww wbr php wbr netMajor implementationsZend Engine HHVM PeachPie Quercus ParrotInfluenced byPerl C C Java 6 Tcl 2 JavaScript 7 InfluencedHack JSP ASP React JSPHP Programming at WikibooksPHP code is usually processed on a web server by a PHP interpreter implemented as a module a daemon or a Common Gateway Interface CGI executable On a web server the result of the interpreted and executed PHP code which may be any type of data such as generated HTML or binary image data would form the whole or part of an HTTP response Various web template systems web content management systems and web frameworks exist that can be employed to orchestrate or facilitate the generation of that response Additionally PHP can be used for many programming tasks outside the web context such as standalone graphical applications 15 and drone control 16 PHP code can also be directly executed from the command line The standard PHP interpreter powered by the Zend Engine is free software released under the PHP License PHP has been widely ported and can be deployed on most web servers on a variety of operating systems and platforms 17 The PHP language has evolved without a written formal specification or standard with the original implementation acting as the de facto standard that other implementations aimed to follow W3Techs reports that as of 23 March 2024 update the four months after the PHP 8 3 release PHP is used by 76 4 of all websites whose programming language could be determined and 57 2 thereof use PHP 7 which is outdated and known to be insecure 18 Additionally PHP 8 0 is no longer supported 19 meaning the vast majority of PHP users utilize outdated versions and well over half of all websites PHP using or not whose programming language could be determined are insecure Contents 1 History 1 1 Early history 1 2 PHP 3 and 4 1 3 PHP 5 1 4 PHP 6 and Unicode 1 5 PHP 7 1 6 PHP 8 1 6 1 Just in time compilation 1 6 2 Addition of the match expression 1 6 3 Type changes and additions 1 6 4 Syntax changes and additions 1 6 5 Standard library changes and additions 1 6 6 Additional changes 1 7 PHP 8 1 1 8 PHP 8 2 1 9 Release history 2 Mascot 3 Syntax 3 1 Data types 3 2 Functions 3 3 PHP objects 3 3 1 Example 4 Implementations 5 Licensing 6 Development and community 7 The PHP Foundation 8 Installation and configuration 9 Use 9 1 Popularity and usage statistics 10 Security 11 See also 12 References 13 Further reading 14 External linksHistory edit nbsp nbsp nbsp Rasmus Lerdorf creator of PHP and Andi Gutmans and Zeev Suraski creators of the Zend Engine Early history edit PHP development began in 1993 9 when Rasmus Lerdorf wrote several Common Gateway Interface CGI programs in C 20 21 which he used to maintain his personal homepage He extended them to work with web forms and to communicate with databases and called this implementation Personal Home Page Forms Interpreter or PHP FI An example of the early PHP syntax 22 lt include text header html gt lt getenv HTTP USER AGENT gt lt if substr exec result Mozilla gt Hey you are using Netscape lt p gt lt endif gt lt sql database select from table where user username gt lt ifless numentries 1 gt Sorry that record does not exist lt p gt lt endif exit gt Welcome lt user gt lt p gt You have lt index 0 gt credits left in your account lt p gt lt include text footer html gt PHP FI could be used to build simple dynamic web applications To accelerate bug reporting and improve the code Lerdorf initially announced the release of PHP FI as Personal Home Page Tools PHP Tools version 1 0 on the Usenet discussion group comp infosystems www authoring cgi on 8 June 1995 1 23 This release included basic functionality such as Perl like variables form handling and the ability to embed HTML By this point the syntax had changed to resemble that of Perl but was simpler more limited and less consistent 12 11 Early PHP was never intended to be a new programming language rather it grew organically with Lerdorf noting in retrospect I don t know how to stop it there was never any intent to write a programming language I have absolutely no idea how to write a programming language I just kept adding the next logical step on the way 24 A development team began to form and after months of work and beta testing officially released PHP FI 2 in November 1997 25 citation needed The fact that PHP was not originally designed but instead was developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters 26 In some cases the function names were chosen to match the lower level libraries which PHP was wrapping 27 while in some very early versions of PHP the length of the function names was used internally as a hash function so names were chosen to improve the distribution of hash values 28 PHP 3 and 4 edit nbsp This is an example of PHP code for the WordPress content management system Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP 3 changing the language s name to the recursive acronym PHP Hypertext Preprocessor 11 29 Afterwards public testing of PHP 3 began and the official launch came in June 1998 Suraski and Gutmans then started a new rewrite of PHP s core producing the Zend Engine in 1999 30 They also founded Zend Technologies in Ramat Gan Israel 11 On 22 May 2000 PHP 4 powered by the Zend Engine 1 0 was released 11 By August 2008 this branch had reached version 4 4 9 PHP 4 is now no longer under development and nor are any security updates planned to be released 31 32 PHP 5 edit On 1 July 2004 PHP 5 was released powered by the new Zend Engine II 11 PHP 5 included new features such as improved support for object oriented programming the PHP Data Objects PDO extension which defines a lightweight and consistent interface for accessing databases and numerous performance enhancements 33 In 2008 PHP 5 became the only stable version under development Late static binding had been missing from previous versions of PHP and was added in version 5 3 34 35 Many high profile open source projects ceased to support PHP 4 in new code from February 5 2008 because of the GoPHP5 initiative 36 provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5 37 38 Over time PHP interpreters became available on most existing 32 bit and 64 bit operating systems either by building them from the PHP source code or by using pre built binaries 39 For PHP versions 5 3 and 5 4 the only available Microsoft Windows binary distributions were 32 bit IA 32 builds 40 41 requiring Windows 32 bit compatibility mode while using Internet Information Services IIS on a 64 bit Windows platform PHP version 5 5 made the 64 bit x86 64 builds available for Microsoft Windows 42 Official security support for PHP 5 6 ended on 31 December 2018 43 PHP 6 and Unicode edit PHP received mixed reviews due to lacking native Unicode support at the core language level 44 45 In 2005 a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP by embedding the International Components for Unicode ICU library and representing text strings as UTF 16 internally 46 Since this would cause major changes both to the internals of the language and to user code it was planned to release this as version 6 0 of the language along with other major features then in development 47 However a shortage of developers who understood the necessary changes and performance problems arising from conversion to and from UTF 16 which is rarely used in a web context led to delays in the project 48 As a result a PHP 5 3 release was created in 2009 with many non Unicode features back ported from PHP 6 notably namespaces In March 2010 the project in its current form was officially abandoned and a PHP 5 4 release was prepared to contain most remaining non Unicode features from PHP 6 such as traits and closure re binding 49 Initial hopes were that a new plan would be formed for Unicode integration but by 2014 none had been adopted citation needed PHP 7 edit During 2014 and 2015 a new major PHP version was developed PHP 7 The numbering of this version involved some debate among internal developers 50 While the PHP 6 Unicode experiments had never been released several articles and book titles referenced the PHP 6 names which might have caused confusion if a new release were to reuse the name 51 After a vote the name PHP 7 was chosen 52 The foundation of PHP 7 is a PHP branch that was originally dubbed PHP next generation phpng It was authored by Dmitry Stogov Xinchen Hui and Nikita Popov 53 and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near complete language compatibility 54 By 14 July 2014 WordPress based benchmarks which served as the main benchmark suite for the phpng project showed an almost 100 increase in performance Changes from phpng make it easier to improve performance in future versions as more compact data structures and other changes are seen as better suited for a successful migration to a just in time JIT compiler 55 Because of the significant changes the reworked Zend Engine was called Zend Engine 3 succeeding Zend Engine 2 used in PHP 5 56 Because of the major internal changes in phpng it must receive a new major version number of PHP rather than a minor PHP 5 release according to PHP s release process 57 Major versions of PHP are allowed to break backward compatibility of code and therefore PHP 7 presented an opportunity for other improvements beyond phpng that require backward compatibility breaks citation needed In particular it involved the following changes Many fatal or recoverable level legacy PHP error mechanisms were replaced with modern object oriented exceptions 58 The syntax for variable dereferencing was reworked to be internally more consistent and complete allowing the use of the operators gt and with arbitrary meaningful left side expressions 59 Support for legacy PHP 4 style constructor methods was deprecated 60 The behavior of the foreach statement was changed to be more predictable 61 Constructors for the few classes built in to PHP which returned null upon failure were changed to throw an exception instead for consistency 62 Several unmaintained or deprecated server application programming interfaces SAPIs and extensions were removed from the PHP core most notably the legacy mysql extension 63 The behavior of the list operator was changed to remove support for strings 64 Support was removed for legacy ASP style delimiters lt and gt and lt script language php gt lt script gt 65 An oversight allowing a switch statement to have multiple default clauses was fixed 66 Support for hexadecimal number support in some implicit conversions from strings to number types was removed 67 The left shift and right shift operators were changed to behave more consistently across platforms 68 Conversions between floating point numbers and integers were changed e g infinity changed to convert to zero and implemented more consistently across platforms 68 69 PHP 7 also included new language features Most notably it introduced return type declarations for functions 70 which complement the existing parameter type declarations and support for the scalar types integer float string and boolean in parameter and return type declarations 71 PHP 8 edit PHP 8 was released on 26 November 2020 and is currently the second most used PHP major version PHP 8 is a major version and has breaking changes from previous versions 72 73 New features and notable changes include Just in time compilation edit Just in time compilation is supported in PHP 8 74 PHP 8 s JIT compiler can provide substantial performance improvements for some use cases 75 76 while PHP developer Nikita Popov stated that the performance improvements for most websites will be less substantial than the upgrade from PHP 5 to PHP 7 77 Substantial improvements are expected more for mathematical type operations than for common web development use cases 77 Additionally the JIT compiler provides the future potential to move some code from C to PHP due to the performance improvements for some use cases 78 Addition of the match expression edit Main article PHP syntax and semantics Match expression PHP 8 introduced the match expression 79 The match expression is conceptually similar to a switch statement and is more compact for some use cases 80 Because match is an expression its result can be assigned to a variable or returned from a function 81 Type changes and additions edit PHP 8 introduced union types a new static return type and a new mixed type 72 Attributes often referred to as annotations in other programming languages were added in PHP 8 which allow metadata to be added to classes 72 throw was changed from being a statement to being an expression 82 This allows exceptions to be thrown in places that were not previously possible 72 Syntax changes and additions edit PHP 8 includes changes to allow alternate more concise or more consistent syntaxes in a number of scenarios For example the nullsafe operator is similar to the null coalescing operator but used when calling methods 83 The following code snippet will not throw an error if getBirthday returns null human readable date user gt getBirthday gt diffForHumans Constructor property promotion has been added as syntactic sugar allowing class properties to be set automatically when parameters are passed into a class constructor 72 This reduces the amount of boilerplate code that must be written citation needed Other minor changes include support for use of class on objects which serves as an alternative for the use of get class 72 non capturing catches in try catch blocks variable syntax tweaks to resolve inconsistencies support for named arguments and support for trailing commas in parameter lists which adds consistency with support for trailing commas in other contexts such as in arrays citation needed Standard library changes and additions edit Weak maps were added in PHP 8 A WeakMap holds references to objects but these references do not prevent such objects from being garbage collected 84 This can provide performance improvements in scenarios where data is being cached this is of particular relevance for object relational mappings ORM 72 Various adjustments to interfaces such as adding support for creating DateTime objects from interfaces and the addition of a Stringable interface that can be used for type hinting citation needed Various new functions including str contains str starts with and str ends with 85 fdiv get debug type and get resource id citation needed Object implementation of token get all citation needed Additional changes edit Type annotations were also added into PHP s C source code itself to allow internal functions and methods to have complete type information in reflection 86 Inheritance with private methods citation needed Abstract methods in traits improvements citation needed PHP 8 1 edit PHP 8 1 was released on November 25 2021 87 It added support for enumerations also called enums declaring properties as readonly which prevents modification of the property after initialization and array unpacking with string keys The new never type can be used to indicate that a function does not return 88 PHP 8 2 edit PHP 8 2 was released on December 8 2022 89 New in this release are readonly classes whose instance properties are implicitly readonly disjunctive normal form DNF types and the random extension which provides a pseudorandom number generator with an object oriented API 90 Release history edit Version Release date Supported until 91 NotesOld version no longer maintained 1 0 8 June 1995 Officially called Personal Home Page Tools PHP Tools This is the first use of the name PHP 11 Old version no longer maintained 2 0 1 November 1997 Officially called PHP FI 2 0 This is the first release that could actually be characterised as PHP being a standalone language with many features that have endured to the present day Old version no longer maintained 3 0 6 June 1998 20 October 2000 91 Development moves from one person to multiple developers Zeev Suraski and Andi Gutmans rewritten the base for this version 11 Old version no longer maintained 4 0 22 May 2000 92 23 June 2001 91 Added more advanced two stage parse execute tag parsing system called the Zend engine 93 Old version no longer maintained 4 1 10 December 2001 94 12 March 2002 91 Introduced superglobals span class nv GET span span class nv POST span span class nv SESSION span etc 93 Old version no longer maintained 4 2 22 April 2002 95 6 September 2002 91 Disabled register globals by default Data received over the network is not inserted directly into the global namespace anymore closing possible security holes in applications 93 Old version no longer maintained 4 3 27 December 2002 96 31 March 2005 91 Introduced the command line interface CLI to supplement the CGI 93 97 Old version no longer maintained 4 4 11 July 2005 98 7 August 2008 91 Fixed a memory corruption bug which required breaking binary compatibility with extensions compiled against PHP version 4 3 x 99 Old version no longer maintained 5 0 13 July 2004 100 5 September 2005 91 Zend Engine II with a new object model 101 Old version no longer maintained 5 1 24 November 2005 102 24 August 2006 91 Performance improvements with the introduction of compiler variables in re engineered PHP Engine 101 Added PHP Data Objects PDO as a consistent interface for accessing databases 103 Old version no longer maintained 5 2 2 November 2006 104 6 January 2011 91 Enabled the filter extension by default Native JSON support 101 Old version no longer maintained 5 3 30 June 2009 105 14 August 2014 91 Namespace support late static bindings jump label limited goto anonymous functions closures PHP archives phar garbage collection for circular references improved Windows support sqlite3 mysqlnd as a replacement for libmysql as the underlying library for the extensions that work with MySQL fileinfo as a replacement for mime magic for better MIME support the Internationalization extension and deprecation of ereg extension Old version no longer maintained 5 4 1 March 2012 106 3 September 2015 91 Trait support short array syntax support Removed items register globals safe mode allow call time pass reference span class nx session register span span class p span span class nx session unregister span span class p span and span class nx session is registered span span class p span Built in web server 107 Several improvements to existing features performance and reduced memory requirements Old version no longer maintained 5 5 20 June 2013 108 10 July 2016 109 Support for generators finally blocks for exceptions handling OpCache based on Zend Optimizer bundled in official distribution 110 Old version no longer maintained 5 6 28 August 2014 111 31 December 2018 109 Constant scalar expressions variadic functions argument unpacking new exponentiation operator extensions of the use statement for functions and constants new phpdbg debugger as a SAPI module and other smaller improvements 112 6 x Not released Abandoned version of PHP that planned to include native Unicode support 113 114 Old version no longer maintained 7 0 3 December 2015 115 10 January 2019 57 Zend Engine 3 performance improvements 55 and 64 bit integer support on Windows 116 uniform variable syntax 59 AST based compilation process 117 added span class nx Closure span span class o span span class na call span span class p span 118 bitwise shift consistency across platforms 119 span class o span null coalesce operator 120 Unicode code point escape syntax 121 return type declarations 70 scalar type integer float string and boolean declarations 71 lt gt spaceship three way comparison operator 122 generator delegation 123 anonymous classes 124 simpler and more consistently available CSPRNG API 125 replacement of many remaining internal PHP errors with the more modern exceptions 58 and shorthand syntax for importing multiple items from a namespace 126 Old version no longer maintained 7 1 1 December 2016 1 December 2019 109 span class nx iterable span type 127 nullable types 128 span class nx void span return type 129 class constant visibility modifiers 130 short list syntax 131 multi catch 132 Old version no longer maintained 7 2 30 November 2017 30 November 2020 109 Object parameter and return type declaration 133 libsodium extension 134 abstract method overriding 135 parameter type widening 136 Old version no longer maintained 7 3 6 December 2018 137 6 December 2021 Flexible Heredoc and Nowdoc syntax 138 support for reference assignment and array deconstruction with span class k list span span class p span 139 PCRE2 support 140 span class nb hrtime span function 141 Old version no longer maintained 7 4 28 November 2019 142 28 November 2022 Typed properties 2 0 143 preloading 144 null coalescing assignment operator 145 improve span class nb openssl random pseudo bytes span 146 weak references 84 foreign function interface FFI 147 always available hash extension 148 password hash registry 149 multibyte string splitting 150 reflection for references 151 unbundle ext wddx 152 new custom object serialization mechanism 153 Old version no longer maintained 8 0 26 November 2020 154 26 November 2023 Just In Time JIT compilation 74 arrays starting with a negative index 155 stricter saner language semantics validation for abstract trait methods 156 saner string to number comparisons 157 saner numeric strings 158 span class nx TypeError span on invalid arithmetic bitwise operators 159 reclassification of various engine errors 160 consistent type errors for internal functions 161 fatal error for incompatible method signatures 162 locale independent float to string conversion 163 variable syntax tweaks 164 attributes 165 166 167 168 named arguments 169 match expression 170 constructor property promotion 171 union types 172 span class nx mixed span type 173 static return type 174 nullsafe operator 83 non capturing catches 175 span class k throw span expression 82 JSON extension is always available 176 Older version yet still maintained 8 1 25 November 2021 177 25 November 2024 Explicit octal integer literal notation 178 enumerations 179 read only properties 180 first class callable syntax 181 span class k new span in initializers 182 pure intersection types 183 span class nx never span return type 184 span class k final span class constraints 185 fibers 186 Older version yet still maintained 8 2 8 December 2022 187 8 December 2025 Readonly classes 188 span class k null span span class k false span and span class k true span as stand alone types 189 190 locale independent case conversion 191 disjunctive normal form types 192 constants in traits 193 Current stable version 8 3 23 November 2023 194 23 November 2026 Typed class constants 195 dynamic class constant fetch 196 span class p span span class nd Override span span class p span attribute 197 deep cloning of read only properties 198 new span class nx json validate span function 199 randomizer additions 200 the command line linter supports multiple filesFuture release 8 4 21 November 2024 201 21 November 2027Legend Old versionOlder version still maintainedLatest versionLatest preview versionFuture releaseBeginning on 28 June 2011 the PHP Development Team implemented a timeline for the release of new versions of PHP 57 Under this system at least one release should occur every month Once per year a minor release should occur which may include new features Every minor release should at least be supported for two years with security and bug fixes followed by at least one year of only security fixes for a total of a three year release process for every minor release No new features unless small and self contained are to be introduced into a minor release during the three year release process Mascot edit nbsp The elePHPant PHP mascotThe mascot of the PHP project is the elePHPant a blue elephant with the PHP logo on its side designed by Vincent Pontier 202 in 1998 203 The PHP letters were forming the shape of an elephant if viewed in a sideways angle 204 The elePHPant is sometimes differently coloured when in plush toy form 205 Many variations of this mascot have been made over the years Only the elePHPants based on the original design by Vincent Pontier are considered official by the community 206 These are collectable and some of them are extremely rare 207 Syntax editMain article PHP syntax and semantics nbsp A Hello World application in PHP 7 4 running on its built in development serverThe following Hello World program is written in PHP code embedded in an HTML document lt DOCTYPE html gt lt html gt lt head gt lt title gt PHP Hello World program lt title gt lt head gt lt body gt lt p gt lt Hello World gt lt p gt lt body gt lt html gt However as no requirement exists for PHP code to be embedded in HTML the simplest version of Hello World may be written like this with the closing tag span class cp gt span omitted as preferred in files containing pure PHP code 208 lt php echo Hello World The PHP interpreter only executes PHP code within its delimiters Anything outside of its delimiters is not processed by PHP although the non PHP text is still subject to control structures described in PHP code The most common delimiters are span class cp lt php span to open and span class cp gt span to close PHP sections The shortened form span class o lt span also exists This short delimiter makes script files less portable since support for them can be disabled in the local PHP configuration and it is therefore discouraged 209 210 Conversely there is no recommendation against the echo short tag span class o lt span 211 Prior to PHP 5 4 0 this short syntax for span class k echo span only works with the short open tag configuration setting enabled while for PHP 5 4 0 and later it is always available 212 213 209 The purpose of all these delimiters is to separate PHP code from non PHP content such as JavaScript code or HTML markup 214 So the shortest Hello World program written in PHP is lt Hello World The first form of delimiters span class cp lt php span and span class cp gt span in XHTML and other XML documents creates correctly formed XML processing instructions 215 This means that the resulting mixture of PHP code and other markups in the server side file is itself well formed XML Variables are prefixed with a dollar symbol and a type does not need to be specified in advance PHP 5 introduced type declarations that allow functions to force their parameters to be objects of a specific class arrays interfaces or callback functions However before PHP 7 type declarations could not be used with scalar types such as integers or strings 71 Below is an example of how PHP variables are declared and initialized lt php name John variable of string type being declared and initialized age 18 variable of integer type being declared and initialized height 5 3 variable of double type being declared and initialized echo name is height m tall n concatenating variables and strings echo name is age years old interpolating variables to string gt Unlike function and class names variable names are case sensitive Both double quoted and heredoc strings provide the ability to interpolate a variable s value into the string 216 PHP treats newlines as whitespace in the manner of a free form language and statements are terminated by a semicolon 217 PHP has three types of comment syntax span class cm span marks block and inline comments span class c1 span or span class c1 span are used for one line comments 218 The echo statement is one of several facilities PHP provides to output text citation needed In terms of keywords and language syntax PHP is similar to C style syntax span class k if span conditions span class k for span and span class k while span loops and function returns are similar in syntax to languages such as C C C Java and Perl citation needed Data types edit PHP is loosely typed It stores integers in a platform dependent range either as a 32 64 or 128 bit signed integer equivalent to the C language long type Unsigned integers are converted to signed values in certain situations which is different behaviour to many other programming languages 219 Integer variables can be assigned using decimal positive and negative octal hexadecimal and binary notations citation needed Floating point numbers are also stored in a platform specific range They can be specified using floating point notation or two forms of scientific notation 220 PHP has a native Boolean type that is similar to the native Boolean types in Java and C Using the Boolean type conversion rules non zero values are interpreted as true and zero as false as in Perl and C 220 The null data type represents a variable that has no value NULL is the only allowed value for this data type 220 Variables of the resource type represent references to resources from external sources These are typically created by functions from a particular extension and can only be processed by functions from the same extension examples include file image and database resources 220 Arrays can contain elements of any type that PHP can handle including resources objects and even other arrays Order is preserved in lists of values and in hashes with both keys and values and the two can be intermingled 220 PHP also supports strings which can be used with single quotes double quotes nowdoc or heredoc syntax 221 The Standard PHP Library SPL attempts to solve standard problems and implements efficient data access interfaces and classes 222 Functions edit PHP defines a large array of functions in the core language and many are also available in various extensions these functions are well documented online PHP documentation 223 However the built in library has a wide variety of naming conventions and associated inconsistencies as described under history above Custom functions may be defined by the developer function myAge int birthYear string calculate the age by subtracting the birth year from the current year yearsOld date Y birthYear return the age in a descriptive string return yearsOld yearsOld 1 year years echo I am currently myAge 1995 old As of 2024 the output of the above sample program is I am currently 29 years old In lieu of function pointers functions in PHP can be referenced by a string containing their name In this manner normal PHP functions can be used for example as callbacks or within function tables 224 User defined functions may be created at any time without being prototyped 223 224 Functions may be defined inside code blocks permitting a run time decision as to whether or not a function should be defined There is a function exists function that determines whether a function with a given name has already been defined Function calls must use parentheses with the exception of zero argument class constructor functions called with the PHP operator new in which case parentheses are optional citation needed Since PHP 4 0 1 create function a thin wrapper around eval allowed normal PHP functions to be created during program execution it was deprecated in PHP 7 2 and removed in PHP 8 0 225 in favor of syntax for anonymous functions or closures 226 that can capture variables from the surrounding scope which was added in PHP 5 3 Shorthand arrow syntax was added in PHP 7 4 227 function getAdder x return fn y gt x y adder getAdder 8 echo adder 2 prints 10 In the example above getAdder function creates a closure using passed argument span class nv x span which takes an additional argument span class nv y span and returns the created closure to the caller Such a function is a first class object meaning that it can be stored in a variable passed as a parameter to other functions etc 228 Unusually for a dynamically typed language PHP supports type declarations on function parameters which are enforced at runtime This has been supported for classes and interfaces since PHP 5 0 for arrays since PHP 5 1 for callables since PHP 5 4 and scalar integer float string and boolean types since PHP 7 0 71 PHP 7 0 also has type declarations for function return types expressed by placing the type name after the list of parameters preceded by a colon 70 For example the getAdder function from the earlier example could be annotated with types like so in PHP 7 function getAdder int x Closure return fn int y int gt x y adder getAdder 8 echo adder 2 prints 10 echo adder null throws an exception because an incorrect type was passed adder getAdder would also throw an exception By default scalar type declarations follow weak typing principles So for example if a parameter s type is int PHP would allow not only integers but also convertible numeric strings floats or booleans to be passed to that function and would convert them 71 However PHP 7 has a strict typing mode which when used disallows such conversions for function calls and returns within a file 71 PHP objects edit Basic object oriented programming functionality was added in PHP 3 and improved in PHP 4 11 This allowed for PHP to gain further abstraction making creative tasks easier for programmers using the language Object handling was completely rewritten for PHP 5 expanding the feature set and enhancing performance 229 In previous versions of PHP objects were handled like value types 229 The drawback of this method was that code had to make heavy use of PHP s reference variables if it wanted to modify an object it was passed rather than creating a copy of it In the new approach objects are referenced by handle and not by value citation needed PHP 5 introduced private and protected member variables and methods along with abstract classes final classes abstract methods and final methods It also introduced a standard way of declaring constructors and destructors similar to that of other object oriented languages such as C and a standard exception handling model Furthermore PHP 5 added interfaces and allowed for multiple interfaces to be implemented There are special interfaces that allow objects to interact with the runtime system Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach language construct There is no virtual table feature in the engine so static variables are bound with a name instead of a reference at compile time 230 If the developer creates a copy of an object using the reserved word clone the Zend engine will check whether a clone method has been defined If not it will call a default clone which will copy the object s properties If a clone method is defined then it will be responsible for setting the necessary properties in the created object For convenience the engine will supply a function that imports the properties of the source object so the programmer can start with a by value replica of the source object and only override properties that need to be changed 231 The visibility of PHP properties and methods is defined using the keywords public private and protected The default is public if only var is used var is a synonym for public Items declared public can be accessed everywhere protected limits access to inherited classes and to the class that defines the item private limits visibility only to the class that defines the item 232 Objects of the same type have access to each other s private and protected members even though they are not the same instance citation needed Example edit The following is a basic example of object oriented programming in PHP 8 lt php abstract class User protected string name public function construct string name make first letter uppercase and the rest lowercase this gt name ucfirst strtolower name public function greet string return Hello my name is this gt name abstract public function job string class Student extends User public function construct string name private string course parent construct name public function job string return I learn this gt course class Teacher extends User public function construct string name private array teachingCourses parent construct name public function job string return I teach implode this gt teachingCourses students new Student Alice Computer Science new Student Bob Computer Science new Student Charlie Business Studies teachers new Teacher Dan Computer Science Information Security new Teacher Erin Computer Science 3D Graphics Programming new Teacher Frankie Online Marketing Business Studies E commerce foreach students teachers as users echo users 0 class s n array walk users function User user echo user gt greet user gt job n This program outputs the following Students Hello my name is Alice I learn Computer Science Hello my name is Bob I learn Computer Science Hello my name is Charlie I learn Business Studies Teachers Hello my name is Dan I teach Computer Science Information Security Hello my name is Erin I teach Computer Science 3D Graphics Programming Hello my name is Frankie I teach Online Marketing Business Studies E commerceImplementations editThe only complete PHP implementation is the original known simply as PHP It is the most widely used and is powered by the Zend Engine To disambiguate it from other implementations it is sometimes unofficially called Zend PHP The Zend Engine compiles PHP source code on the fly into an internal format that it can execute thus it works as an interpreter 233 234 It is also the reference implementation of PHP as PHP has no formal specification and so the semantics of Zend PHP define the semantics of PHP Due to the complex and nuanced semantics of PHP defined by how Zend works it is difficult for competing implementations to offer complete compatibility citation needed PHP s single request per script execution model and the fact that the Zend Engine is an interpreter leads to inefficiency as a result various products have been developed to help improve PHP performance In order to speed up execution time and not have to compile the PHP source code every time the web page is accessed PHP scripts can also be deployed in the PHP engine s internal format by using an opcode cache which works by caching the compiled form of a PHP script opcodes in shared memory to avoid the overhead of parsing and compiling the code every time the script runs An opcode cache Zend Opcache is built into PHP since version 5 5 235 Another example of a widely used opcode cache is the Alternative PHP Cache APC which is available as a PECL extension 236 While Zend PHP is still the most popular implementation several other implementations have been developed Some of these are compilers or support JIT compilation and hence offer performance benefits over Zend PHP at the expense of lacking full PHP compatibility citation needed Alternative implementations include the following HHVM HipHop Virtual Machine developed at Facebook and available as open source it converts PHP code into a high level bytecode commonly known as an intermediate language which is then translated into x86 64 machine code dynamically at runtime by a just in time JIT compiler resulting in up to 6 performance improvements 237 However since version 7 2 Zend has outperformed HHVM 238 and HHVM 3 24 is the last version to officially support PHP 239 HipHop developed at Facebook and available as open source it transforms the PHP scripts into C code and then compiles the resulting code reducing the server load up to 50 In early 2013 Facebook deprecated it in favour of HHVM due to multiple reasons including deployment difficulties and lack of support for the whole PHP language including the create function and eval constructs 240 Parrot a virtual machine designed to run dynamic languages efficiently the cross translator Pipp transforms the PHP source code into the Parrot intermediate representation which is then translated into the Parrot s bytecode and executed by the virtual machine PeachPie a second generation compiler to NET Common Intermediate Language CIL bytecode built on the Roslyn platform successor of Phalanger sharing several architectural components Phalanger compiles PHP into Net Common Intermediate Language bytecode predecessor of PeachPie Quercus compiles PHP into Java bytecodeLicensing editMain article PHP License PHP is free software released under the PHP License which stipulates that 241 Products derived from this software may not be called PHP nor may PHP appear in their name without prior written permission from group php net You may indicate that your software works in conjunction with PHP by saying Foo for PHP instead of calling it PHP Foo or phpfoo This restriction on the use of PHP makes the PHP License incompatible with the General Public License GPL while the Zend License is incompatible due to an advertising clause similar to that of the original BSD license 242 Development and community editPHP includes various free and open source libraries in its source distribution or uses them in resulting PHP binary builds PHP is fundamentally an Internet aware system with built in modules for accessing File Transfer Protocol FTP servers and many database servers including PostgreSQL MySQL Microsoft SQL Server and SQLite which is an embedded database LDAP servers and others Numerous functions are familiar to C programmers such as those in the stdio family are available in standard PHP builds 243 PHP allows developers to write extensions in C to add functionality to the PHP language PHP extensions can be compiled statically into PHP or loaded dynamically at runtime Numerous extensions have been written to add support for the Windows API process management on Unix like operating systems multibyte strings Unicode cURL and several popular compression formats Other PHP features made available through extensions include integration with Internet Relay Chat IRC dynamic generation of images and Adobe Flash content PHP Data Objects PDO as an abstraction layer used for accessing databases 244 245 246 247 248 249 250 and even speech synthesis Some of the language s core functions such as those dealing with strings and arrays are also implemented as extensions 251 The PHP Extension Community Library PECL project is a repository for extensions to the PHP language 252 Some other projects such as Zephir provide the ability for PHP extensions to be created in a high level language and compiled into native PHP extensions Such an approach instead of writing PHP extensions directly in C simplifies the development of extensions and reduces the time required for programming and testing 253 By December 2018 the PHP Group consisted of ten people Thies C Arntzen Stig Bakken Shane Caraveo Andi Gutmans Rasmus Lerdorf Sam Ruby Sascha Schumann Zeev Suraski Jim Winstead and Andrei Zmievski 254 Zend Technologies provides a PHP Certification based on PHP 7 255 exam and previously based on PHP 5 5 for programmers to become certified PHP developers The PHP Foundation editPHP nbsp FormationNovember 22 2021 2 years ago 2021 11 22 FounderAutomattic Laravel Acquia Zend Private Packagist Symfony Craft CMS Tideways PrestaShop JetBrains 256 Websitehttps thephp foundationOn 26 November 2021 the JetBrains blog announced the creation of The PHP Foundation which will sponsor the design and development of PHP 257 Year Commits Reviews RFCs2022 258 683 283 82023 259 784 702 17The foundation hires Core Developers to work on the PHP language s core repository Roman Pronskiy a member of the foundation s board said that they aim to pay market salaries to developers 260 The response to the foundation has mostly been positive with the foundation being praised for better supporting the language and helping to stop the decrease in the language s popularity 261 262 However it has also been criticised for adding breaking changes to minor versions of PHP such as in PHP 8 2 where initialising members of a class out with the original class scope would cause depreciation errors 263 these changes impacted a number of open source projects including WordPress 264 Installation and configuration edit nbsp Example output of the phpinfo function in PHP 7 1There are two primary ways for adding support for PHP to a web server as a native web server module or as a CGI executable PHP has a direct module interface called server application programming interface SAPI which is supported by many web servers including Apache HTTP Server Microsoft IIS and iPlanet Web Server Some other web servers such as OmniHTTPd support the Internet Server Application Programming Interface ISAPI which is Microsoft s web server module interface If PHP has no module support for a web server it can always be used as a Common Gateway Interface CGI or FastCGI processor in that case the web server is configured to use PHP s CGI executable to process all requests to PHP files 265 PHP FPM FastCGI Process Manager is an alternative FastCGI implementation for PHP bundled with the official PHP distribution since version 5 3 3 266 When compared to the older FastCGI implementation it contains some additional features mostly useful for heavily loaded web servers 267 When using PHP for command line scripting a PHP command line interface CLI executable is needed PHP supports a CLI server application programming interface SAPI since PHP 4 3 0 268 The main focus of this SAPI is developing shell applications using PHP There are quite a few differences between the CLI SAPI and other SAPIs although they do share many of the same behaviours 269 PHP has a direct module interface called SAPI for different web servers 270 in case of PHP 5 and Apache 2 0 on Windows it is provided in form of a DLL file called php5apache2 dll 271 which is a module that among other functions provides an interface between PHP and the web server implemented in a form that the server understands This form is what is known as a SAPI citation needed There are different kinds of SAPIs for various web server extensions For example in addition to those listed above other SAPIs for the PHP language include the Common Gateway Interface and command line interface 270 272 PHP can also be used for writing desktop graphical user interface GUI applications by using the PHP GTK extension PHP GTK is not included in the official PHP distribution 265 and as an extension it can be used only with PHP versions 5 1 0 and newer The most common way of installing PHP GTK is by compiling it from the source code 273 When PHP is installed and used in cloud environments software development kits SDKs are provided for using cloud specific features citation needed For example Amazon Web Services provides the AWS SDK for PHP 274 Microsoft Azure can be used with the Windows Azure SDK for PHP 275 Numerous configuration options are supported affecting both core PHP features and extensions 276 277 Configuration file php ini is searched for in different locations depending on the way PHP is used 278 The configuration file is split into various sections 279 while some of the configuration options can be also set within the web server configuration 280 Use edit nbsp A broad overview of the LAMP software bundle displayed here together with SquidPHP is a general purpose scripting language that is especially suited to server side web development in which case PHP generally runs on a web server Any PHP code in a requested file is executed by the PHP runtime usually to create dynamic web page content or dynamic images used on websites or elsewhere 281 It can also be used for command line scripting and client side graphical user interface GUI applications PHP can be deployed on most web servers many operating systems and platforms and can be used with many relational database management systems RDBMS Most web hosting providers support PHP for use by their clients It is available free of charge and the PHP Group provides the complete source code for users to build customize and extend for their own use 17 nbsp Dynamic web page example of server side scripting PHP and MySQL Originally designed to create dynamic web pages PHP now focuses mainly on server side scripting 282 and it is similar to other server side scripting languages that provide dynamic content from a web server to a client such as Python Microsoft s ASP NET Sun Microsystems JavaServer Pages 283 and a href Mod perl html title Mod perl mod perl a PHP has also attracted the development of many software frameworks that provide building blocks and a design structure to promote rapid application development RAD citation needed Some of these include PRADO CakePHP Symfony CodeIgniter Laravel Yii Framework Phalcon and Laminas offering features similar to other web frameworks The LAMP architecture has become popular in the web industry as a way of deploying web applications 284 PHP is commonly used as the P in this bundle alongside Linux Apache and MySQL although the P may also refer to Python Perl or some mix of the three Similar packages WAMP and MAMP are also available for Windows and macOS with the first letter standing for the respective operating system Although both PHP and Apache are provided as part of the macOS base install users of these packages seek a simpler installation mechanism that can be more easily kept up to date citation needed For specific and more advanced usage scenarios PHP offers a well defined and documented way for writing custom extensions in C or C 285 286 287 288 289 290 291 non primary source needed Besides extending the language itself in form of additional libraries extensions are providing a way for improving execution speed where it is critical and there is room for improvements by using a true compiled language 292 293 PHP also offers well defined ways for embedding itself into other software projects That way PHP can be easily used as an internal scripting language for another project also providing tight interfacing with the project s specific internal data structures 294 PHP received mixed reviews due to lacking support for multithreading at the core language level 295 though using threads is made possible by the pthreads PECL extension 296 297 A command line interface php cli and two ActiveX Windows Script Host scripting engines for PHP have been produced citation needed Popularity and usage statistics edit Usage share of PHP versions on 23 March 2024 four months after PHP 8 3 s release 18 298 299 300 301 PHP 8 3 2 10 of PHP 8 0 56 PHP 8 2 18 3 of PHP 8 4 85 PHP 8 1 40 7 of PHP 8 10 79 PHP 8 0 38 9 of PHP 8 10 31 PHP 7 4 69 0 of PHP 7 39 47 PHP 7 3 13 2 of PHP 7 7 55 PHP 7 2 9 60 of PHP 7 5 49 PHP 7 1 3 90 of PHP 7 2 23 PHP 7 0 4 30 of PHP 7 2 46 PHP 5 6 54 0 of PHP 5 8 7480 PHP 5 5 8 40 of PHP 5 1 3608 PHP 5 4 15 4 of PHP 5 2 4948 PHP 5 3 14 9 of PHP 5 2 4138 PHP 5 2 6 80 of PHP 5 1 1016 PHP 5 1 0 40 of PHP 5 0 0648 PHP 5 0 0 10 of PHP 5 0 0162 PHP 4 4 78 7 of PHP 4 0 1574 PHP 4 3 18 5 of PHP 4 0 0370 PHP 4 2 1 60 of PHP 4 0 0032 PHP 4 1 0 80 of PHP 4 0 0016 PHP 4 0 0 30 of PHP 4 0 0006 PHP is used for Web content management systems including MediaWiki 302 WordPress 303 Joomla 304 Drupal 305 Moodle 306 eZ Publish eZ Platform and SilverStripe 307 As of January 2013 update PHP was used in more than 240 million websites 39 of those sampled and was installed on 2 1 million web servers 308 As of 23 March 2024 update four months after PHP 8 3 s release PHP is used as the server side programming language on 76 4 of websites where the language could be determined PHP 7 is the most used version of the language with 57 2 of websites using PHP being on that version while 26 6 use PHP 8 16 2 use PHP 5 and 0 2 use PHP 4 18 Security editIn 2019 11 of all vulnerabilities listed by the National Vulnerability Database were linked to PHP 309 historically about 30 of all vulnerabilities listed since 1996 in this database are linked to PHP Technical security flaws of the language itself or of its core libraries are not frequent 22 in 2009 about 1 of the total although PHP applies to about 20 of programs listed 310 Recognizing that programmers make mistakes some languages include taint checking to automatically detect the lack of input validation which induces many issues Such a feature is being developed for PHP 311 but its inclusion into a release has been rejected several times in the past 312 313 There are advanced protection patches such as Suhosin and Hardening Patch specially designed for web hosting environments 314 Historically old versions of PHP had some configuration parameters and default values for such runtime settings that made some PHP applications prone to security issues Among these a href Magic quotes html title Magic quotes magic quotes gpc a and register globals 315 configuration directives were the best known the latter made any URL parameters become PHP variables opening a path for serious security vulnerabilities by allowing an attacker to set the value of any uninitialized global variable and interfere with the execution of a PHP script Support for magic quotes and register globals settings has been deprecated since PHP 5 3 0 and removed from PHP 5 4 0 316 Another example for the potential runtime settings vulnerability comes from failing to disable PHP execution for example by using the engine configuration directive 317 for the directory where uploaded files are stored enabling it can result in the execution of malicious code embedded within the uploaded files 318 319 320 The best practice is to either locate the image directory outside of the document root available to the web server and serve it via an intermediary script or disable PHP execution for the directory which stores the uploaded files citation needed Also enabling the dynamic loading of PHP extensions via enable dl configuration directive 321 in a shared web hosting environment can lead to security issues 322 323 Implied type conversions that result in different values being treated as equal sometimes against the programmer s intent can lead to security issues For example the result of the comparison 0e1234 0 is true because strings that are parsable as numbers are converted to numbers in this case the first compared value is treated as scientific notation having the value 0 101234 which is zero Errors like this resulted in authentication vulnerabilities in Simple Machines Forum 324 Typo3 325 and phpBB 326 when MD5 password hashes were compared The recommended way is to use hash equals for timing attack safety a href Strcmp html class mw redirect title Strcmp strcmp a or the identity operator as 0e1234 0 results in false 327 In a 2013 analysis of over 170 000 website defacements published by Zone H the most frequently 53 used technique was the exploitation of file inclusion vulnerability mostly related to insecure usage of the PHP language constructs include require and allow url fopen 328 329 As of 23 March 2024 update 4 months after PHP 8 3 release W3Techs reports that 83 9 of websites using PHP use versions 8 0 or older which are no longer supported by The PHP Development Team 330 PHP Version 5 is still used by 16 2 of all websites 299 It is highly recommended to migrate to PHP 8 1 or later and use random int 331 instead of rand 332 or mt rand 333 as the latter functions are not cryptographically secure There are two attacks that can be performed over PHP entropy sources seed attack and state recovery attack citation needed With current when GPU technologies an attacker can perform up to 230 MD5 calculations per second with a 250 GPU while with an additional 500 can reach up to 232 calculations 334 In combination with a birthday attack this can lead to serious security vulnerabilities citation needed See also edit nbsp Computer programming portal nbsp Free and open source software portalComparison of programming languages List of Apache MySQL PHP packages List of PHP accelerators List of PHP editors PEAR PHP Extension and Application Repository PHP accelerator Template processor XAMPP free and open source cross platform web server solution stack package Zend ServerReferences edit a b Lerdorf Rasmus June 8 1995 Announce Personal Home Page Tools PHP Tools Retrieved 7 June 2011 a b Lerdorf Rasmus 2007 04 26 PHP on Hormones history of PHP presentation by Rasmus Lerdorf given at the MySQL Conference in Santa Clara California The Conversations Network Archived from the original on 2019 01 06 Retrieved 2009 12 11 PHP News Archive 2024 www php net PHP Function arguments Manual secure php net PHP Release Archives museum museum php net PHP Preface Manual Stogov Dmitry dstogov December 4 2015 It s not a secret that some PHP7 optimization ideas came from HHVM LuaJIT and V8 Thank you HipHopVM SaraMG php7thankyou Tweet via Twitter PHP Hypertext Preprocessor www php net Retrieved 2020 02 12 a b Krill Paul 2013 11 18 Believe the hype PHP founder backs Facebook s HipHop technology InfoWorld Retrieved 2022 10 13 Announce Personal Home Page Tools PHP Tools groups google com Retrieved 2022 11 03 a b c d e f g h i History of PHP and related projects The PHP Group Retrieved 2008 02 25 a b History of PHP php net Olsson Mikael 2013 09 04 PHP Quick Scripting Reference Apress ISBN 978 1 4302 6284 8 PHP Manual Preface www php net Introduction What can PHP do PHP Manual Retrieved 2009 03 05 helicopter Port of node ar drone which allows user to control a Parrot AR Drone over PHP jolicode php ar drone JoliCode 2019 01 11 retrieved 2019 02 23 a b Embedding PHP in HTML O Reilly 2001 05 03 Archived from the original on 2008 02 19 Retrieved 2008 02 25 a b c Usage statistics of PHP for websites W3Techs World Wide Web Technology Surveys W3Techs Retrieved 23 March 2024 Usage Statistics 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original on 2013 09 21 Retrieved 2013 09 22 enable dl configuration directive PHP Runtime Configuration PHP net Retrieved 2014 02 13 PHP function reference dl PHP net Retrieved 2013 09 22 My host won t fix their Trojan WebHosting Talk Retrieved 2013 09 22 Raz0r 25 January 2013 Simple Machines Forum lt 2 0 3 Admin Password Reset a href Template Cite web html title Template Cite web cite web a CS1 maint numeric names authors list link Nibble Security TYPO3 SA 2010 020 TYPO3 SA 2010 022 EXPLAINED Kriptostojkost i nebezopasnoe sravnenie Ahack ru in Russian Comparison operators PHP net Krawczyk Pawel 2013 Most common attacks on web applications IPSec pl Archived from the original on 2015 04 15 Retrieved 2015 04 15 Krawczyk Pawel 2013 So what are the most critical application flaws On new OWASP Top 10 IPSec pl Retrieved 2015 04 15 Usage Statistics and Market Share of PHP for Websites March 2024 w3techs com Retrieved 2024 03 23 PHP Random int Manual PHP Rand Manual PHP Mt rand Manual I Forgot Your Password Randomness Attacks Against PHP Applications www readkong com Further reading editListen to this article 35 minutes source source nbsp This audio file was created from a revision of this article dated 23 November 2011 2011 11 23 and does not reflect subsequent edits Audio help More spoken articles Ford Paul June 11 2015 What is Code Bloomberg Businessweek What s the Absolute Minimum I Must Know About PHP External links editOfficial website nbsp PHP at Curlie PHP at Wikipedia s sister projects nbsp Media from Commons nbsp Textbooks from Wikibooks nbsp Resources from Wikiversity nbsp Documentation from MediaWiki Retrieved from https en wikipedia org w index php title PHP amp oldid 1218920119 PHP 7, wikipedia, wiki, book, books, library,

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