PHP developers create programs and applications using this server-side scripting language. PHP was designed for web development but is also used as a general-purpose programming language. PHP commands can be embedded directly into a HTML source document rather than calling an external file to process data. PHP developers frequently work in linux environments with an Apache Server and MySQL database data storage (known as the LAMP archetypal model). Many popular web content management systems are written in PHP including MediaWiki, Joomla, WordPress and Drupal, so some PHP developers works on projects based on those frameworks, maintaining or extending functionality.