MediaWiki - Open Source Wiki

MediaWiki is a open source wiki package written in PHP, originally for use on Wikipedia. Developed by the Wikimedia Foundation and others, it is used to run all of the Foundation’s projects, including Wikipedia, Wiktionary and Wiki news. Numerous other wikis around the world also use it to power their websites. It is written in the PHP programming language and uses a backend database. The software's code is structured functionally. The software is optimized to correctly and efficiently handle projects of all sizes, including the largest wikis, which can have terabytes of content and hundreds of thousands of hits per second. Because Wikipedia is one of the world's largest websites, achieving scalability through multiple layers of caching and database replication has also been a major concern for developers. Wikipedia and other Wikimedia projects continue to define a large part of the requirement set for Media Wiki.