PhpWiki is a WikiWikiWeb clone in PHP. A WikiWikiWeb is a site where anyone can edit the pages through an HTML form. Multiple storage backends, dynamic hyperlinking, themeable, scriptable by plugins, full authentication, ACL's.
PhpWiki 1.2.11 adds small fixes from user patches. I just forgot to release them in the last years, sorry.
Note that 1.2.x is the old-stable branch, which is not in active development since 2001 anymore. 1.3.x is the active branch with all the features.