PHP is a general-purpose server-side scripting language, widely used in web development. It stands for PHP: Hypertext Preprocessor, a recursive acronym, just like how GNU is a recursive acronym for 'GNU's not UNIX'.

PHP grew out of a set of Perl/CGI scripts written by Rasmus Lerdof to track visitors to his online résumé. It was then known as Personal Homepage Tools/Form Interpreter, shortened to PHP/FI. Its version 1.0 was released in June 1995.

Rasmus Lerdorf. Public Domain