serializing DomDocument objects.

Hi all. I was just wondering why my attempts to serialize DomDocument objects have failed? Is this a bug, or am I doing something wrong? I am also unable to save DomDocument's in session variables (not that I want to do that or anything, just testing). I get "Warning: Couldn't fetch domdocument in..." when i try to use the object after storing it. I would like to be able to serialize DomDocument's to reduce the overhead of creating the DOM Tree for documents that are used often, with the aim of improving the speed of the framework I'm developing. I'm using the PHP5 Beta so what i'm saying may be fixed (if it's a bug in the first place that is) in CVS. Thanks for your cool work. riot.