MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
AMuseWiki - Amusewiki is more than just a wiki engine, it’s also a powerful authoring, archiving and publishing platform.
HelpDocs - Educate your users with a super simple knowledge base that’s built for teams just like yours.
BetterDocs - Create & Manage Knowledge Base Documentation Effectively To Reduce Support Tickets, Increase productivity & User Experience with BetterDocs.
phpMyFAQ - phpMyFAQ is a world’s most popular mobile-friendly, feature-rich and open-sources FAQ software that uses PHP 5.