Larry Garfield points out one of the better resources for those looking to learn about the Standard PHP Library functionality - the tutorial on the Zend Developer Zone.

Of course, the main problem is that the official documentation on it sucks. At best it points to an off-site series of class hierarchies. (Technically it's not off-site, but not internal to the manual.)

The article talks mainly about iterators and some other "goodies" including exceptions and array handling.