PHP is a server-side scripting language most frequently associated with web development but that is also commonly used as a general purpose programming language. PHP is reportedly now installed on over 240 million websites and well over 2 million web servers.

Created by Danish programmer Rasmus Lerdorf in 1995 as a part of a series of CGI Perl scripts he wrote and used to maintain his personal web page, PHP originally stood for personal home page; it now stands for PHP: Hypertext Preprocessor. Basic object-oriented programming functionality was introduced in PHP 3 and refined in PHP 4, while object handling was completely revised for PHP 5, enhancing performance and adding significantly to the object set.

PHP code functions by a PHP code being interpreted by a web server equipped with a PHP processor module, which then generates a webpage based on the PHP code. PHP commands can be directly embedded into an HTML document, rather than calling on an external resource or file to process data. More recent versions of PHP also include a command-line interface ability and can be employed in standalone graphical apps.

Available as free software under the PHP license, PHP can be installed on most web servers, or as a standalone shell on most operating systems.