PHP is a general-purpose server-side scripting language originally designed for Web development to produce dynamic Web pages. It is one of the first developed server-side scripting languages to be embedded into an HTML source document, rather than calling an external file to process data. Ultimately, the code is interpreted by a Web server with a PHP processor module which generates the resulting Web page. It also has evolved to include a command-line interface capability and can be used in standalone graphical applications. PHP can be deployed on most Web servers and also as a standalone shell on almost every operating system and platform free of charge. A competitor to Microsoft's Active Server Pages (ASP) server-side script engine and similar languages, PHP is installed on more than 20 million Web sites and 1 million Web servers.

PHP was originally created by Rasmus Lerdorf in 1995. The main implementation of PHP is now produced by The PHP Group and serves as the formal reference to the PHP language. PHP is free software released under the PHP License, which is incompatible with the GNU General Public License (GPL) due to restrictions on the usage of the term PHP.

Rasmus Lerdorf (born 22 November 1968 in Qeqertarsuaq, Greenland) is a Danish programmer with Canadian citizenship and is most notable as the creator of the PHP scripting language. He authored the first two versions. Lerdorf also participated in the development of later versions of PHP led by a group of developers including Jim Winstead (who later created blo.gs), Stig Bakken, Shane Caraveo, Andi Gutmans and Zeev Suraski.

He graduated from King City Secondary School in 1988, and in 1993 he graduated from the University of Waterloo with a Bachelor of Applied Science in Systems Design Engineering. He contributed to the Apache HTTP Server and he added the LIMIT clause to the mSQL Database in 1995.

From September 2002 to November 6, 2009, he was employed by Yahoo! Inc. as an Infrastructure Architecture Engineer. In 2010, he joined WePay in order to develop their API. As of 2011, he is a roving consultant for startups. On February 22nd, 2012, he announced on Twitter that he had joined Etsy.

Lerdorf is a frequent speaker at Open Source conferences around the world. During his keynote presentation at OSCMS 2007, he presented a security vulnerability in each of the projects represented at the conference that year.