PHP application for knowledge management?

Hi All, Just wondering if anyone can recommend an open php source application suitable for knowledge management for a small development team? We have 3 coders with different responsibilities, but often have to cover each other if unexpected things happen. We're hoping to implement a knowledge management tool of some sort in which we can store business logic, code snippets, back-end table / stored procedure descriptions and so forth. We're hoping to find something that allows us to extensively categorize / keyword entries, in which content is easy to maintain, expand etc, and which has extensive search capabilities. Our ultimate (if perhaps unlikely) goal is to be able to place a new coder into our environment with a tool that enables him or her to get up to speed with our environment in the shortest time possible. Any suggestions / pointers welcome! Much warmth, planetthoughtful