New on his blog Matthew Weier O'Phinney has this post looking about using the FilterIterator (from PHP's SPL libraries) to work with (recursive) directory iteration.

I'm currently doing research and prototyping for autoloading alternatives in Zend Framework 2.0. One approach I'm looking at involves creating explicit class/file maps; these tend to be much faster than using the include_path, but do require some additional setup. [...] I'm well aware of RecursiveDirectoryIterator, and planned to use that. However, I also had heard of FilterIterator, and wondered if I could tie that in somehow. In the end, I could, but the solution was non-obvious.

He starts with what he thought he should be able to do with the FilterIterator - pass in a DirectoryIterator to be able to filter them recursively. Unfortunately this only worked for the first level, so he looked else where. His solution ultimately involved passing in a RecursiveIteratorIterator instance into the DirectoryIterator that contained his RecursiveDirectoryIterator. He includes a full code example in the post showing how to locate a certain file/class recursively inside a directory.