In a new post to his blog today Brandon Savage has taken a look at the SPL ArrayObject component including how it's handled in a PHP5 OOP kind of world.
ArrayObject is an object that is designed to behave exactly like an array. If that seems confusing, don’t worry, it’s not. ArrayObject is an object. It follows all the rules of how objects work. But it’s designed to implicitly behave like an array for all intents and purposes, including being used in a foreach loop, and accessing it’s properties just like you would access the values in an array.
He includes a code snippet showing how the ArrayObject can be used and explains that, since it's an object and not an array, the "copy, not duplicate" handling applies to it. You get the best of two worlds - the ease of an array and the power of an object (plus there's some performance improvements too).