PHPCI is a free and open source continuous integration tool specifically designed for PHP. Built with simplicity in mind and featuring integrations with all of your favourite testing tools, we've created the very best platform for testing your PHP projects.

Over at Sitepoint Peter Nijssen wrote a good overview of the offered functionality.

I've been playing around with the self-hosted version.  It comes with a bunch of plugins that are installed by default.

I can recommended it if you, like me, are starting out with CI.