PHP

PHP is a general-purpose scripting language geared towards web development.<ref>Template:Cite web</ref> It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995.<ref name="Krill-2013">Template:Cite web</ref><ref>Template:Cite web</ref> The PHP reference implementation is now produced by the PHP Group.<ref name="The PHP Group">Template:Cite web</ref> PHP was originally an abbreviation of Personal Home Page,<ref name="php.net-3">Template:Cite web</ref><ref>Template:Cite book</ref> but it now stands for the recursive backronym PHP: Hypertext Preprocessor.<ref>PHP Manual: Preface, PHP.</ref>

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 codeTemplate:Em dashwhich may be any type of data, such as generated HTML or binary image dataTemplate:Em dashwould 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 programming tasks outside the web context, though most non-web uses are rare. 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.<ref name="O'Reilly-2001" />

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 Template:As of (about three years since PHP 7 was discontinued and 23 months after the PHP 8.3 release), unsupported versions such as PHP 7 are still used by well over half of PHP websites, which are outdated and known to be insecure.<ref name="www.php.net">Template:Cite web</ref><ref name="W3Techs – World Wide Web Technology Surveys" /> Those included the 9.7% of PHP websites using the even more outdated (discontinued for 7 years) and insecure PHP 5, released over two decades ago, and the no-longer supported PHP 8.0 is also very popular, so a large majority of PHP websites do not use supported versions.

History

Early history (1993 to 1997)

PHP development began in 1993<ref name="Krill-2013" /> when Rasmus Lerdorf wrote several Common Gateway Interface (CGI) programs in C,<ref name="Lerdorf-2012">Template:Cite web</ref><ref>Template:Cite web</ref> 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:<ref>Template:Cite web</ref>

<syntaxhighlight lang="html">

Hey, you are using Netscape!

Sorry, that record does not exist

Welcome !

You have credits left in your account.

</syntaxhighlight> 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.<ref name="Lerdorf-1995">Template:Cite web</ref><ref>Template:Cite newsgroup</ref> 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.<ref name="php.net-3" /><ref name="The PHP Group" /> 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."<ref name="Rasmus Lerdorf-2003">Template:Cite web</ref> A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997.<ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref> In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping",<ref>Template:Cite web</ref> 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.<ref name="Rasmus Lerdorf-2013">Template:Cite newsgroup</ref>

PHP 3 and 4 (1998 to 2004)

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.<ref name="The PHP Group" /><ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref> They also founded Zend Technologies in Ramat Gan, Israel.<ref name="The PHP Group" />

On 22 May 2000, PHP 4.0, powered by the Zend Engine 1.0, was released.<ref name="The PHP Group" /> 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.<ref name="The PHP Group-2007a">Template:Cite web</ref><ref>Template:Cite web</ref>

Early PHP 5 (2004 to 2006)

On 1 July 2004, PHP 5.0 was released, powered by the new Zend Engine 2.0.<ref name="The PHP Group" /> PHP 5.0 included significant changes to the language, most notably an overhauled approach to object-oriented programming, as well as iterators and exceptions.<ref>Template:Cite web</ref>

PHP 5.1 and PHP 5.2 were released the following years, adding smaller improvements and new features, such as the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases) In 2008, PHP 5.x became the only stable version under development.

Many high-profile open-source projects ceased to support PHP 4 in new code from February 5, 2008, because of the GoPHP5 initiative,<ref name="GoPHP5">Template:Cite web</ref> provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.<ref name="GoPHP5 Press Release">Template:Cite web</ref><ref>Template:Cite web</ref>

PHP 6 and Unicode

PHP's native string functions worked only on raw bytes, making use with multibyte character encodings difficult.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> 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.<ref>Template:Cite mailing list</ref> 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.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref> As a result, a PHP 5.3 release was created in 2009, and 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.<ref>Template:Cite mailing list</ref> Initial hopes were that a new plan would be formed for Unicode integration, but by 2014 none had been adopted.Template:Citation needed

Later PHP 5 (2009 to 2014)

Because it contained features originally intended to be part of 6.0, PHP 5.3 was a significant release, adding support for namespaces, closures, late static binding,<ref>Template:Cite web</ref><ref>Template:Cite web</ref> and many fixes and improvements to standard functions.

With the Unicode branch officially abandoned, a new release process was adopted in 2011, planning a yearly release cycle, and a clear distinction between "feature releases" (x.y.z to x.y+1.z) and "major releases" (x.y.z to x+1.0.0).<ref name="PHP-2011" /> Remaining features which had been planned for the 6.0 release were included in PHP 5.4, released in March 2012, such as trait support and a new "short array syntax". This was followed by more incremental changes in PHP 5.5 (June 2013) and 5.6 (August 2014).

For PHP versions 5.3 and 5.4, the only available Microsoft Windows binary distributions were 32-bit IA-32 builds,<ref>Template:Cite web</ref><ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref>

Official security support for PHP 5.6 ended on 31 December 2018.<ref>Template:Cite web</ref>

PHP 7.x (2015 to 2019)

During 2014 and 2015, a new major PHP version was developed, PHP 7.0. The numbering of this version involved some debate among internal developers.<ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref> After a vote, the name PHP 7 was chosen.<ref>Template:Cite web</ref>

The foundation of PHP 7.0 was a PHP branch that was originally dubbed PHP next generation (phpng). It was written by Dmitry Stogov, Xinchen Hui and Nikita Popov,<ref>Template:Cite web</ref> and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility.<ref>Template:Cite web</ref> 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.<ref name="php.net-7">Template:Cite web</ref> Because of the significant changes, the reworked Zend Engine was called Zend Engine 3, succeeding Zend Engine 2 used in PHP 5.x.<ref name="github.com-2014">Template:Cite web</ref>

PHP 7.0 also included changes which were not backwards compatible, as allowed for "major versions" under the versioning scheme agreed in 2011.<ref name="PHP-2011" /> Changes to the core language included a more consistent handling of variable dereferencing,<ref name="php.net-2014b">Template:Cite web</ref> a more predictable behavior of the foreach statement,<ref>Template:Cite web</ref> and platform consistency of bitwise shifts<ref name="php.net-5" /> and floating-point to integer conversion.<ref name="php.net-5">Template:Cite web</ref><ref>Template:Cite web</ref> Several unmaintained or deprecated server application programming interfaces (SAPIs) and extensions were removed from the PHP core, most notably the legacy mysql extension.<ref>Template:Cite web</ref> Other legacy features were also removed, such as ASP-style delimiters <% and %> and <script language="php"> ... </script>.<ref>Template:Cite web</ref>

PHP 7.0 marked the beginning of an expansion in PHP's type system. In PHP 5.x, only function parameters could have type declarations, but this was extended to function return types in 7.0.,<ref name="php.net-2015a">Template:Cite web</ref> and object properties in 7.4<ref name="PHP: rfc:typed_properties_v2">Template:Cite web</ref> The types expressible also expanded, with scalar types (integer, float, string, and boolean) in 7.0;<ref name="php.net-2015b">Template:Cite web</ref> Template:Code type,<ref name="PHP: rfc:iterable">Template:Cite web</ref> nullable types,<ref name="PHP: rfc:nullable_types">Template:Cite web</ref> and [[Void type|Template:Code return type]].<ref name="PHP: rfc:void_return_type">Template:Cite web</ref> all in 7.1; and the Template:Code type in 7.2<ref name="PHP: rfc:object-typehint">Template:Cite web</ref>

Other changes in this period aimed to add expressiveness to the language, such as the Template:Code (null coalesce)<ref name="PHP: rfc:isset_ternary">Template:Cite web</ref> and Template:Code "spaceship" three-way comparison<ref name="Combined Comparison Spaceship Ope">Template:Cite web</ref> operators in 7.0; new syntax for array derefencing<ref name="PHP: rfc:short_list_syntax">Template:Cite web</ref> and catching multiple exception types<ref name="PHP: rfc:multiple-catch">Template:Cite web</ref> in PHP 7.1; more flexible Heredoc and Nowdoc syntax<ref name="PHP: rfc:flexible_heredoc_nowdoc_sy">Template:Cite web</ref> in 7.3; and the null-coalescing assignment operator<ref name="ReferenceA">Template:Cite web</ref> in 7.4.

PHP 8.x (2020 onwards)

PHP 8.0 was released on 26 November 2020, as a major version with breaking changes from previous versions.<ref name="Brent">Template:Cite web</ref><ref name="PHP">Template:Cite web</ref>

One of the most high-profile changes was the addition of a JIT compiler, which can provide substantial performance improvements for some use cases.<ref name="Brent-2">Template:Cite web</ref><ref>Template:Cite web</ref> Substantial improvements are expected more for mathematical-type operations than for common web-development use cases.<ref name="Popov-2020">Template:Cite webTemplate:Cbignore</ref> Additionally, the performance advantages of the JIT compiler provides the future potential to move some code from C to PHP.<ref name="Daniele-2020">Template:Cite web</ref>

A significant addition to the language in 8.0 is attributes which allow metadata to be added to program elements such as classes, methods, and parameters.<ref name="Brent" /> Later versions added built-in attributes which change the behaviour of the language, such as the Template:Code attribute in PHP 8.2,<ref>Template:Cite web</ref> Template:Code attribute in PHP 8.3,<ref name=":0" /> Template:Code attribute in PHP 8.4,<ref>Template:Cite web</ref> and the Template:Code and Template:Code attributes in PHP 8.5.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>

A significant extension to the language's type system is the addition of composite types: union types in PHP 8.0 (e.g. Template:Code meaning "either integer or string),<ref name=":1" /> intersection types in PHP 8.1 (e.g. Template:Code meaning the value must implement both the Traversable and Countable interfaces),<ref name=":2" /> and disjunctive normal form (DNF) types in PHP 8.2 (unions of intersections, such as Template:Code).<ref name=":3" /> Additional special type keywords have also been added, such as Template:Code and Template:Code in PHP 8.0,<ref name="Brent" /> Template:Code (a bottom type indicating that a function never returns) in PHP 8.1,<ref name=":4" /> and Template:Code, Template:Code, and Template:Code as stand-alone types in PHP 8.2.<ref name=":5" /><ref name=":6" />

The addition of a rich type system is part of a general trend towards a stricter language, and PHP 8.0 included breaking changes to the handling of string to number comparisons,<ref name=":7" /> numeric strings,<ref name=":8" /> and incompatible method signatures.<ref name=":9" /> Later versions have introduced deprecation notices for behaviour which is planned as a breaking change in a future major version, such as passing null to non-nullable internal function parameters<ref>Template:Cite web</ref> and referring to properties which have not been declared on the class.<ref>Template:Cite web</ref>

Release history

Version	Release date	Supported until<ref name="php.net-2">Template:Cite web</ref>	Notes
Template:Version	8 June 1995		Officially called "Personal Home Page Tools (PHP Tools)". This is the first use of the name "PHP".<ref name="The PHP Group" />
Template:Version	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.
Template:Version	6 June 1998	20 October 2000<ref name="php.net-2" />	Development moves from one person to multiple developers. Zeev Suraski and Andi Gutmans rewritten the base for this version.<ref name="The PHP Group" />
Template:Version	22 May 2000<ref>Template:Cite web</ref>	23 June 2001<ref name="php.net-2" />	Added more advanced two-stage parse/execute tag-parsing system called the Zend engine.<ref name="The PHP Group-2008">Template:Cite web</ref>
Template:Version	10 December 2001<ref>Template:Cite web</ref>	12 March 2002<ref name="php.net-2" />	Introduced "superglobals" (Template:Code, Template:Code, Template:Code, etc.)<ref name="The PHP Group-2008" />
Template:Version	22 April 2002<ref>Template:Cite web</ref>	6 September 2002<ref name="php.net-2" />	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.<ref name="The PHP Group-2008" />
Template:Version	27 December 2002<ref>Template:Cite web</ref>	31 March 2005<ref name="php.net-2" />	Introduced the command-line interface (CLI), to supplement the CGI.<ref name="The PHP Group-2008" /><ref name="PHP Manual-2">Template:Cite web</ref>
Template:Version	11 July 2005<ref>Template:Cite web</ref>	7 August 2008<ref name="php.net-2" />	Fixed a memory corruption bug, which required breaking binary compatibility with extensions compiled against PHP version 4.3.x.<ref>Template:Cite web</ref>
Template:Version	13 July 2004<ref>Template:Cite web</ref>	5 September 2005<ref name="php.net-2" />	Zend Engine II with a new object model.<ref name="The PHP Group-2007">Template:Cite web</ref>
Template:Version	24 November 2005<ref>Template:Cite web</ref>	24 August 2006<ref name="php.net-2" />	Performance improvements with the introduction of compiler variables in re-engineered PHP Engine.<ref name="The PHP Group-2007" /> Added PHP Data Objects (PDO) as a consistent interface for accessing databases.<ref name="The PHP Group-2011">Template:Cite web</ref>
Template:Version	2 November 2006<ref>Template:Cite web</ref>	6 January 2011<ref name="php.net-2" />	Enabled the filter extension by default. Native JSON support.<ref name="The PHP Group-2007" />
Template:Version	30 June 2009<ref>Template:Cite web</ref>	14 August 2014<ref name="php.net-2" />	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.
Template:Version	1 March 2012<ref>Template:Cite web</ref>	3 September 2015<ref name="php.net-2" />	Trait support, short array syntax support. Removed items: register_globals, safe_mode, allow_call_time_pass_reference, Template:Code, Template:Code and Template:Code. Built-in web server.<ref>Template:Cite web</ref> Several improvements to existing features, performance and reduced memory requirements.
Template:Version	20 June 2013<ref>Template:Cite web</ref>	10 July 2016<ref name="php.net-8">Template:Cite web</ref>	Support for generators, finally blocks for exceptions handling, OpCache (based on Zend Optimizer+) bundled in official distribution.<ref name="php.net-9">Template:Cite web</ref>
Template:Version	28 August 2014<ref>Template:Cite web</ref>	31 December 2018<ref name="php.net-8" />	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.<ref name="php.net-10">Template:Cite web</ref>
6.x	Template:N/a	Template:N/a	Abandoned version of PHP that planned to include native Unicode support.<ref>Template:Cite web</ref><ref>Template:Cite news</ref>
Template:Version	3 December 2015<ref name="php.net-2018">Template:Cite web</ref>	10 January 2019<ref name="PHP-2011" />	Zend Engine 3 (performance improvements<ref name="php.net-7" /> and 64-bit integer support on Windows<ref>Template:Cite web</ref>), uniform variable syntax,<ref name="php.net-2014b" /> AST-based compilation process,<ref>Template:Cite web</ref> added Template:Code,<ref>Template:Cite web</ref> bitwise shift consistency across platforms,<ref>Template:Cite web</ref> Template:Code (null coalesce) operator,<ref name="PHP: rfc:isset_ternary"/> Unicode code point escape syntax,<ref>Template:Cite web</ref> return type declarations,<ref name="php.net-2015a" /> scalar type (integer, float, string and boolean) declarations,<ref name="php.net-2015b" /> <=> "spaceship" three-way comparison operator,<ref name="Combined Comparison Spaceship Ope"/> generator delegation,<ref>Template:Cite web</ref> anonymous classes,<ref>Template:Cite web</ref> simpler and more consistently available CSPRNG API,<ref>Template:Cite web</ref> replacement of many remaining internal PHP "errors" with the more modern exceptions,<ref name="php.net">Template:Cite web</ref> and shorthand syntax for importing multiple items from a namespace.<ref>Template:Cite web</ref>
Template:Version	1 December 2016	1 December 2019<ref name="php.net-8" />	Template:Code type,<ref name="PHP: rfc:iterable"/> nullable types,<ref name="PHP: rfc:nullable_types"/> [[Void type|Template:Code return type]],<ref name="PHP: rfc:void_return_type"/> class constant visibility modifiers,<ref>Template:Cite web</ref> short list syntax,<ref name="PHP: rfc:short_list_syntax"/> multi-catch<ref name="PHP: rfc:multiple-catch"/>
Template:Version	30 November 2017	30 November 2020<ref name="php.net-8" />	Template:Code parameter and return type declaration,<ref name="PHP: rfc:object-typehint"/> libsodium extension,<ref>Template:Cite web</ref> abstract method overriding,<ref>Template:Cite web</ref> parameter type widening<ref>Template:Cite web</ref>
Template:Version	6 December 2018<ref>Template:Cite web</ref>	6 December 2021	Flexible Heredoc and Nowdoc syntax,<ref name="PHP: rfc:flexible_heredoc_nowdoc_sy"/> support for reference assignment and array deconstruction with Template:Code,<ref>Template:Cite web</ref> PCRE2 support,<ref>Template:Cite web</ref> Template:Code function<ref>Template:Cite web</ref>
Template:Version	28 November 2019<ref>Template:Cite web</ref>	28 November 2022	Typed properties,<ref name="PHP: rfc:typed_properties_v2"/> preloading,<ref>Template:Cite web</ref> null-coalescing assignment operator,<ref name="ReferenceA"/> improve Template:Code,<ref>Template:Cite web</ref> weak references,<ref name="wiki.php.net-3">Template:Cite web</ref> foreign function interface (FFI),<ref>Template:Cite web</ref> always available hash extension,<ref>Template:Cite web</ref> password hash registry,<ref>Template:Cite web</ref> multibyte string splitting,<ref>Template:Cite web</ref> reflection for references,<ref>Template:Cite web</ref> unbundle ext/wddx,<ref>Template:Cite web</ref> new custom object serialization mechanism<ref>Template:Cite web</ref>
Template:Version	26 November 2020<ref>Template:Cite web</ref>	26 November 2023	Just-In-Time (JIT) compilation,<ref name="wiki.php.net-2">Template:Cite web</ref> arrays starting with a negative index,<ref>Template:Cite web</ref> stricter/saner language semantics (validation for abstract trait methods),<ref>Template:Cite web</ref> saner string to number comparisons,<ref name=":7">Template:Cite web</ref> saner numeric strings,<ref name=":8">Template:Cite web</ref> Template:Code on invalid arithmetic/bitwise operators,<ref>Template:Cite web</ref> reclassification of various engine errors,<ref>Template:Cite web</ref> consistent type errors for internal functions,<ref>Template:Cite web</ref> fatal error for incompatible method signatures,<ref name=":9">Template:Cite web</ref> locale-independent float to string conversion,<ref>Template:Cite web</ref> variable syntax tweaks,<ref>Template:Cite web</ref> attributes,<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref> named arguments,<ref>Template:Cite web</ref> match expression,<ref>Template:Cite web</ref> constructor property promotion,<ref>Template:Cite web</ref> union types,<ref name=":1">Template:Cite web</ref> Template:Code type,<ref>Template:Cite web</ref> static return type,<ref>Template:Cite web</ref> nullsafe operator,<ref name="wiki.php.net">Template:Cite web</ref> non-capturing catches,<ref>Template:Cite web</ref> Template:Code expression,<ref name="wiki.php.net-4">Template:Cite web</ref> JSON extension is always available.<ref name="Andre">Template:Cite web</ref>
Template:Version	25 November 2021<ref>Template:Cite web</ref>	31 December 2025	Explicit octal integer literal notation,<ref>Template:Cite web</ref> enumerations,<ref>Template:Cite web</ref> read-only properties,<ref>Template:Cite web</ref> first-class callable syntax,<ref>Template:Cite web</ref> Template:Code in initializers,<ref>Template:Cite web</ref> pure intersection types,<ref name=":2">Template:Cite web</ref> Template:Code return type,<ref name=":4">Template:Cite web</ref> Template:Code class constraints,<ref>Template:Cite web</ref> fibers<ref>Template:Cite web</ref>
Template:Version	8 December 2022<ref>Template:Cite web</ref>	31 December 2026	Readonly classes,<ref>Template:Cite web</ref> Template:Code, Template:Code, and Template:Code as stand-alone types,<ref name=":5">Template:Cite web</ref><ref name=":6">Template:Cite web</ref> locale-independent case conversion,<ref>Template:Cite web</ref> disjunctive normal form types,<ref name=":3">Template:Cite web</ref> constants in traits<ref>Template:Cite web</ref>
Template:Version	23 November 2023<ref>Template:Cite web</ref>	31 December 2027	Typed class constants,<ref>Template:Cite web</ref> dynamic class constant fetch,<ref>Template:Cite web</ref> Template:Code attribute,<ref name=":0">Template:Cite web</ref> deep-cloning of read-only properties,<ref>Template:Cite web</ref> new Template:Code function,<ref>Template:Cite web</ref> randomizer additions,<ref>Template:Cite web</ref> the command-line linter supports multiple files
Template:Version	21 November 2024<ref>Template:Cite web</ref>	31 December 2028	Property hooks, asymmetric visibility, an updated DOM API, performance improvements, bug fixes, and general cleanup.
Template:Version	20 November 2025<ref>Template:Cite web</ref>	31 December 2029	Pipe Operator Template:Code<ref>Template:Cite web</ref>
Template:Version

Beginning on 28 June 2011, the PHP Development Team implemented a timeline for the release of new versions of PHP.<ref name="PHP-2011">Template:Cite web</ref> 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. A 2024 RFC extended the length of the security fix only period to two years, fixed all end of life dates to 31 December, and removed the exception that allowed for "small and self-contained" features to be introduced in patch versions.<ref name="rfc-release-cycle-update" />

Mascot

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<ref>Template:Cite web</ref> in 1998.<ref>Template:Cite web</ref> "The (PHP) letters were forming the shape of an elephant if viewed in a sideways angle."<ref>Template:Cite web</ref>

The elePHPant is sometimes differently coloured when in plush toy form.<ref>Template:Cite web</ref> Many variations of this physical mascot have been made over the years. Only the elePHPants based on the original design by Vincent Pontier are considered official by the community.<ref>Template:Cite web</ref> These are collectable and some of them are extremely rare.<ref>Template:Cite web</ref>

Syntax

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:

<syntaxhighlight lang="html+php" highlight="7-9"> <!DOCTYPE html> <html>

   <head>
       <title>PHP "Hello, World!" program</title>
   </head>
   <body>

<?= 'Hello, World!' ?>

   </body>

</html> </syntaxhighlight>

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 <syntaxhighlight lang="PHP" inline="">?></syntaxhighlight> omitted as preferred in files containing pure PHP code.<ref>Template:Cite web</ref>

<syntaxhighlight lang="php5"> <?php echo 'Hello, World!'; </syntaxhighlight>

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 <syntaxhighlight lang="PHP" inline=""><?php</syntaxhighlight> to open and <syntaxhighlight lang="PHP" inline="">?></syntaxhighlight> to close PHP sections. The shortened form <syntaxhighlight lang="PHP" inline=""><?</syntaxhighlight> 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.<ref name="php.net-2008" /><ref name="The PHP Group-3">Template:Cite web</ref> Conversely, there is no recommendation against the echo short tag <syntaxhighlight lang="PHP" inline=""><?=</syntaxhighlight>.<ref>Template:Cite web</ref> Prior to PHP 5.4.0, this short syntax for <syntaxhighlight lang="php" inline="">echo</syntaxhighlight> only works with the short_open_tag configuration setting enabled, while for PHP 5.4.0 and later it is always available.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref name="php.net-2008">Template:Cite web</ref> The purpose of all these delimiters is to separate PHP code from non-PHP content, such as JavaScript code or HTML markup.<ref>Template:Cite web</ref> So the shortest "Hello, World!" program written in PHP is: <syntaxhighlight lang="html+php"> <?='Hello, World!'; </syntaxhighlight> The first form of delimiters, <syntaxhighlight lang="PHP" inline><?php</syntaxhighlight> and <syntaxhighlight lang="PHP" inline>?></syntaxhighlight>, in XHTML and other XML documents, creates correctly formed XML processing instructions.<ref>Template:Cite web</ref> This means that the resulting mixture of PHP code and other markups in the server-side file is itself well-formed XML.

Template:Anchor 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.<ref name="php.net-2015b" />

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

<syntaxhighlight lang="php"> <?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

?> </syntaxhighlight>

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.<ref>Template:Cite web</ref> PHP treats newlines as whitespace in the manner of a free-form language, and statements are terminated by a semicolon.<ref>Template:Cite web</ref> PHP has three types of comment syntax: <syntaxhighlight lang="PHP" inline>/* */</syntaxhighlight> marks block and inline comments; <syntaxhighlight lang="PHP" inline>//</syntaxhighlight> or <syntaxhighlight lang="PHP" inline>#</syntaxhighlight> are used for one-line comments.<ref>Template:Cite web</ref> The echo statement is one of several facilities PHP provides to output text.Template:Citation needed

In terms of keywords and language syntax, PHP is similar to C-style syntax. <syntaxhighlight lang="PHP" inline>if</syntaxhighlight> conditions, <syntaxhighlight lang="PHP" inline>for</syntaxhighlight> and <syntaxhighlight lang="PHP" inline>while</syntaxhighlight> loops and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.Template:Citation needed

Data types

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.<ref>Template:Cite web</ref> Integer variables can be assigned using decimal (positive and negative), octal, hexadecimal, and binary notations.<ref>Template:Cite web</ref>

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.<ref name="The PHP Group-2">Template:Cite web</ref> 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++.<ref name="The PHP Group-2" />

The null data type represents a variable that has no value; NULL is the only allowed value for this data type.<ref name="The PHP Group-2" />

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.<ref name="The PHP Group-2" />

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.<ref name="The PHP Group-2" /> PHP also supports strings, which can be used with single quotes, double quotes, nowdoc or heredoc syntax.<ref>Template:Cite web</ref>

The Standard PHP Library (SPL) attempts to solve standard problems and implements efficient data access interfaces and classes.<ref>Template:Cite web</ref>

Functions

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.<ref name="php.net-2014a" /> 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:

<syntaxhighlight lang="php"> 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.'; </syntaxhighlight>

As of 2025, the output of the above sample program is "I am currently {{#expr: 2025 - 1995}} 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.<ref name="php.net-2014c" /> User-defined functions may be created at any time without being prototyped.<ref name="php.net-2014a">Template:Cite web</ref><ref name="php.net-2014c">Template:Cite web</ref> 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.Template: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<ref>Template:Cite web</ref> in favor of syntax for anonymous functions or "closures"<ref>Template:Cite web</ref> that can capture variables from the surrounding scope, which was added in PHP 5.3. Shorthand arrow syntax was added in PHP 7.4:<ref>Template:Cite web</ref>

<syntaxhighlight lang="php"> function getAdder($x) {

   return fn($y) => $x + $y;

}

$adder = getAdder(8); echo $adder(2); // prints "10" </syntaxhighlight>

In the example above, getAdder() function creates a closure using passed argument Template:Code, which takes an additional argument Template:Code, 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.<ref>Template:Cite web</ref>

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.<ref name="php.net-2015b" /> 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.<ref name="php.net-2015a" /> For example, the getAdder function from the earlier example could be annotated with types like so in PHP 7:

<syntaxhighlight lang="php"> 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 </syntaxhighlight>

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.<ref name="php.net-2015b" /> However, PHP 7 has a "strict typing" mode which, when used, disallows such conversions for function calls and returns within a file.<ref name="php.net-2015b" />

PHP objects

Basic object-oriented programming functionality was added in PHP 3 and improved in PHP 4.<ref name="The PHP Group" /> 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.<ref name="mjtsai.com" /> In previous versions of PHP, objects were handled like value types.<ref name="mjtsai.com">Template:Cite web</ref> 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.<ref>Template:Cite web</ref>

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.<ref name="The PHP Group-4">Template:Cite web</ref>

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.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref> Objects of the same type have access to each other's private and protected members even though they are not the same instance.<ref>Template:Cite web</ref>

Example

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

<syntaxhighlight lang="php" line> <?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";
   });

} </syntaxhighlight>

This program outputs the following:

Implementations

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.<ref>Template:Cite web</ref><ref>Template:Cite book</ref> 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.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref> Another example of a widely used opcode cache is the Alternative PHP Cache (APC), which is available as a PECL extension.<ref>Template:Cite web</ref>

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.Template: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.<ref>Template:Cite web</ref> However, since version 7.2 Zend has outperformed HHVM,<ref>Template:Cite web</ref> and HHVM 3.24 is the last version to officially support PHP.<ref>Template:Cite web</ref>
  • 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.<ref>Template:Cite web</ref>
• 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

PHP is free software released under the PHP License, which stipulates that:<ref>Template:Cite web</ref>

This restriction on the use of "PHP" makes the PHP License incompatible with the GNU General Public License (GPL), while the Zend License is incompatible due to an advertising clause similar to that of the original BSD license.<ref>Template:Cite web</ref>

Development and community

Template:See also 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.<ref>Template:Cite web</ref>

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,<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite magazine</ref> and even speech synthesis. Some of the language's core functions, such as those dealing with strings and arrays, are also implemented as extensions.<ref>Template:Cite web</ref> The PHP Extension Community Library (PECL) project is a repository for extensions to the PHP language.<ref>Template:Cite web</ref> Most of the community focuses on web development, and PHP running server side (though also serving JavaScript for the client side), and some exceptional uses are for e.g. standalone graphical applications (with PHP-GTK unmaintained now for over a decade),<ref>Template:Cite web</ref> and even drone control.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref>

Zend Technologies provides a PHP Certification based on PHP 8<ref>Template:Cite web</ref> exam (and previously based on PHP 7 and 5.5) for programmers to become certified PHP developers.

The PHP Foundation

Template:Infobox organization On 26 November 2021, the JetBrains blog announced the creation of The PHP Foundation, which will sponsor the design and development of PHP.<ref>Template:Cite web</ref>

Year	Commits	Reviews	RFCs
2022<ref>Template:Cite web</ref>	683	283	8
2023<ref>Template:Cite web</ref>	784	702	17
2024<ref>Template:Cite web</ref>	1976	1278	13

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.<ref>Template:Cite news</ref>

The response to the foundation has been largely positive, with commentators praising its role in ensuring the continued development of PHP and helping to stabilise the language's community and popularity.<ref name="JetBrains2021">Template:Cite web</ref><ref name="Register2021">Template:Cite news</ref>

Germany's Sovereign Tech Fund provided more than 200,000 Euros to support the PHP Foundation.<ref>Template:Cite web</ref>

Installation and configuration

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.<ref name="php.net-4">Template:Cite web</ref>

PHP-FPM (FastCGI Process Manager) is an alternative FastCGI implementation for PHP, bundled with the official PHP distribution since version 5.3.3.<ref>Template:Cite web</ref> When compared to the older FastCGI implementation, it contains some additional features, mostly useful for heavily loaded web servers.<ref>Template:Cite web</ref>

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.<ref>Template:Cite web</ref> 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.<ref>Template:Cite web</ref>

PHP has a direct module interface called SAPI for different web servers;<ref name="php.net-6">Template:Cite web</ref> in case of PHP 5 and Apache 2.0 on Windows, it is provided in form of a DLL file called Template:Mono,<ref>Template:Cite web</ref> 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.Template: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.<ref name="php.net-6" /><ref>Template:Cite web</ref>

PHP can also be used for writing desktop graphical user interface (GUI) applications, by using the Template:Cite web or discontinued PHP-GTK extension. PHP-GTK is not included in the official PHP distribution,<ref name="php.net-4" /> 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.<ref>Template:Cite web</ref>

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

• Amazon Web Services provides the AWS SDK for PHP<ref>Template:Cite web</ref>
• Microsoft Azure can be used with the Windows Azure SDK for PHP.<ref>Template:Cite web</ref>

Numerous configuration options are supported, affecting both core PHP features and extensions.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> Configuration file php.ini is searched for in different locations, depending on the way PHP is used.<ref>Template:Cite web</ref> The configuration file is split into various sections,<ref>Template:Cite web</ref> while some of the configuration options can be also set within the web server configuration.<ref>Template:Cite web</ref>

Use

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.<ref>Template:Cite web</ref> 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.<ref name="O'Reilly-2001">Template:Cite web</ref>

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,<ref>Template:Cite web</ref> 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,<ref>Template:Cite web</ref> 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).Template: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.<ref>Template:Cite web</ref> 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.Template: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++.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>Template:Primary source inline 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.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> 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.<ref>Template:Cite book</ref>

PHP received mixed reviews due to lacking support for multithreading at the core language level,<ref>Template:Cite web</ref> though using threads is made possible by the "pthreads" PECL extension.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

A command line interface, php-cli, and two ActiveX Windows Script Host scripting engines for PHP have been produced.Template:Citation needed

Popularity and usage statistics

PHP is used for Web content management systems including MediaWiki,<ref>Template:Cite web</ref> WordPress,<ref>Template:Cite web</ref> Joomla,<ref>Template:Cite web</ref> Drupal,<ref>Template:Cite web</ref> Moodle,<ref>Template:Cite web</ref> eZ Publish, eZ Platform, and SilverStripe.<ref>Template:Cite web</ref>

Template:As of, PHP was used in more than 240 million websites (39% of those sampled) and was installed on 2.1 million web servers.<ref>Template:Cite web</ref>

Template:As of (six months after PHP 8.4's release), PHP is used as the server-side programming language on 74.2% of websites where the language could be determined; PHP 8 is the most used version of the language with 45.3% of websites using PHP being on that version, while 43.7% use PHP 7, 10.9% use PHP 5 and 0.1% use PHP 4.<ref name="W3Techs – World Wide Web Technology Surveys">Template:Cite web</ref>

Security

In 2019, 11% of all vulnerabilities listed by the National Vulnerability Database were linked to PHP;<ref name="National Vulnerability Database">Template:Cite web</ref> 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).<ref name="PHP-2012">Template:Cite web</ref> 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 has been proposed for PHP in the past, but either been rejected or the proposal abandoned.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Third-party projects such as Suhosin<ref>Template:Cite web</ref> and Snuffleupagus<ref>Template:Cite web</ref> aim to remove or change dangerous parts of the language.

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<ref name="PHP Manual-3">Template:Cite web</ref> 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.<ref name="PHP Manual">Template:Cite web</ref>

Another example for the potential runtime-settings vulnerability comes from failing to disable PHP execution (for example by using the engine configuration directive)<ref>Template:Cite web</ref> for the directory where uploaded files are stored; enabling it can result in the execution of malicious code embedded within the uploaded files.<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref> 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.Template:Citation needed

Also, enabling the dynamic loading of PHP extensions (via enable_dl configuration directive)<ref>Template:Cite web</ref> in a shared web hosting environment can lead to security issues.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

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 Template:Nowrap 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 (Template:Val), which is zero. Errors like this resulted in authentication vulnerabilities in Simple Machines Forum,<ref>Template:Cite news</ref> Typo3<ref>Template:Cite web</ref> and phpBB<ref>Template:Cite web</ref> when MD5 password hashes were compared. The recommended way is to use hash_equals() (for timing attack safety), strcmp or the identity operator (===), as Template:Nowrap results in false.Template:Citation needed

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.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Cryptographic security

PHP includes rand()<ref>Template:Cite web</ref> and mt_rand()<ref>Template:Cite web</ref> functions which use a pseudorandom number generator, and are not cryptographically secure. As of version 8.1, the random_int() function is included, which uses a cryptographically secure source of randomness provided by the system.<ref>Template:Cite web</ref>

There are two attacks that can be performed over PHP entropy sources: "seed attack" and "state recovery attack".Template:Citation needed As of 2012, a $250 GPU can perform up to 2Template:Sup MD5 calculations per second, while a $750 GPU can perform four times as many calculations at the same time.<ref>Template:Cite web</ref> In combination with a "birthday attack" this can lead to serious security vulnerabilities.Template:Citation needed

Long-term support

The PHP development team provides official bug fixes for two years following release of each minor version followed by another two years where only security fixes are released.<ref name="rfc-release-cycle-update">Template:Cite web</ref> After this, the release is considered end of life and no longer officially supported.

Extended long-term support beyond this is available from commercial providers, such as Zend and others<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

See also

• Comparison of programming languages
• List of Apache–MySQL–PHP packages
• List of PHP accelerators
• List of PHP editors
• List of PHP software and tools
• PEAR (PHP Extension and Application Repository)
• PHP accelerator
• Template processor
• XAMPP (free and open-source cross-platform web server solution stack package)
• Zend Server

Further reading

• Template:Cite journal

External links

• Template:Official website