I am looking for a piece of software, hopefully PHP, that can manage a documentation site for software. I want something similar to http://www.clientexec.com/docs (powered by a Wakka - which doesn't work with Safe Mode because they were too lazy to work with unregistered globals). I don't want a PHPDoc generator or anything of the sort, just something that manages a help system so-to-speak.

Has any either programmed one of these or knows where I can purchase/download one?