If you've ever wanted to give back to the PHP project, but weren't sure quite how, Rafael Dohms has written up a post to make one of the options much easier to get into - writing PHPT tests for the PHP language.
The beauty about PHPT is that you need to know very little other than writing PHP code. A little knowledge into the inner workings of PHP will of course help you in finding areas of code that need testing, and how best to test them, but just knowing PHP is enough to start.
He leads you through a five step process that'll have you up and writing tests in no time - setting up your environment, looking for something to test, writing and executing a test and submitting the results back to the PHP project. He sprinkles in a few code bits and screenshots to help point you in the right direction.