We have created an open-source Ruby-on-Rails-like light-weight PHP Framework called PHPrecious here. Feel free to check it out and play around with it. There is a full demo included in the demos folder.
Every component in the framework is as loosely coupled as possible. You can use it as a web framework as well as for server-site php scripts and daemons.
It mostly lacks proper documentation at this moment. Hope the demo helps you a little.