On DZone.com today Giorgio Sironi has posted a "cheat sheet" to help you correlate the functionality of two PHP unit testing tools - PHPUnit vs Phake (for mocking objects).
Benjamin Eberlei introduced me to Phake with his recent article: it is a Composer-ready PHP library that integrates easily with PHPUnit and provides an independent Test Doubles framework, capable of producing Stubs, Mocks, and Spies. The syntax and object model reminds me of Mockito, the Java Test Double framework from the authors of Growing Object-Oriented Software. I like tools that do one thing and do it well, and after experimenting with Phake I'm using it on all new code.
He compares the two tools on a few different pieces of functionality including creating stubs, mocks and spies. Sample code is included for both sides. It's not a detailed guide by any means, but it can give you a better picture of how the two compare.