I have to say, one of my favorite parts of simplexml, is the array / object duality.

Attributes are accessed via => , and children are accessed via []. This would have been awesome for fapi, if you could actually use it as a

language feature. (I think they probably implement it via magic callbacks, and that only handles the calling, not the definitions.)

However, it's impossible to serialize (cache, or conversely store in the session) simplexml objects, so you always have the xml parsing overhead.

The other interesting thing we could look at is exceptions. Error handling in PHP has _long_ been one of my sore points with the language.