Dokuwiki is a PHP based wiki. This website is run on Dokuwiki, for an example implementation. It's a very flexible piece of software, and I highly recommend it. You can get it from http://www.dokuwiki.org/DokuWiki.

This website is using a modified version of the Battlehorse template. I modified the template to be more like a Content Management System rather than a Wiki, since that is my primary use case.

I am also using the Gallery plugin (look at the Pannonia repair Manual in the motorcycle section)