On the SitePoint PHP Blog a tutorial has been posted recently about having some fun with array interfaces via some of the functionality provided through the SPL (Standard PHP Library).

As a programmer who works with different languages every day, I find a lot of joy in learning how things are done differently in other languages and seeing if I can do the same in PHP. One thing I liked in particular in Python was how one can emulate features of native data types in custom classes. [...] I thought it would be nice if you could do the same in PHP on an instance of your custom classes and not only arrays. PHP lets us do this with array interfaces.

He illustrates his intent with some basic Python functionality and shows how to use various PHP interfaces to achieve a similar functionality. He talks about SPL interfaces like Countable, ArrayAccess and Iterator to make objects more useful in an array handling environment. His example uses the idea of a set of user's tweets (from Twitter) and shows the implementation of these three interfaces.