On PHPBuilder.com today there's a new tutorial from Jason Gilmore about using the SPL with different data types to more effectively work with them more effectively.

One great way to incorporate more OOP into your applications is through the Standard PHP Library (SPL), a powerful yet largely unknown extension made part of the official PHP language with the PHP 5.0 release. [...] In this tutorial I'll introduce you to several of my favorite SPL iterators, providing you with the basis from which you can continue your own exploration. Following several examples, I'll conclude with a brief introduction to other key SPL features.

He looks at how to use the ArrayIterator, DirectoryIterator, SimpleXMLIterator and mentions some of the other handlers for things like advanced data structures, exceptions and more file handling.