On Software.Newsforge.com there's a review of a PHP framework today - dotProject 2.0.1.

DotProject is a robust Web-based project management framework written in PHP that allows users to schedule, plan, and staff projects. It's not a perfect application, but its extensive functionality and ease of use make its shortcomings easy to overlooked.

I looked at the latest dotProject, version 2.0.1, which was released in April. DotProject runs on a typical LAMP (Linux, Apache, MySQL, PHP) server setup, but version 2.0.1 doesn't work properly with PHP 5 (there are some workarounds, but it's not worth the trouble), so you'll need to stick with PHP 4 (the most recent version 4.3.11 is a good choice).

From the sound of things, the reviewer seems impressed with the "staggering amount of useful functionality" that it provides, thought it's not without issues.

On the whole, DotProject is a solid multi-user project management tool that stands on its own merits.