To further previous comments and drive the point home:
What makes SimpleXMLElement tricky to work with is that it feels and behaves like an object, but is actually a system RESOURCE, (specifically a libxml resource).
That's why you can't store a SimpleXMLElement to $_SESSION or perform straight comparison operations on node values without first casting them to some type of object. $_SESSION expects to store 'an object' and comparison operators expect to compare 2 'objects' and SimpleXMLElements are not objects.
When you echo or print a node's value, PHP converts the value (a resource) into a string object for you. It's a time saver for sure, but can fool you into thinking that your SimpleXMLElement is an object.
Hope this helps clarify
