MediaWiki is an open wiki software protected by the GNU license. It is written in PHP and uses MySQL or PostgreSQL relational database management system
MediaWiki; Since version 1.7, PHP 5 support is required. If you are using an older version of PHP you will have to use MediaWiki version 1.6.10.
At first MediaWiki was developed for Wikipedia, a free encyclopedia, but later it became the most widely used wiki software. Today, all Wikimedia Foundation projects, all sites hosted on Wikia, and many other wikis are used.
It is also used by companies for corporate information management or content management purposes. The largest example is Novell, which manages its publicly-large sites with this system (changes are publicly closed).