I put this form online so you can try the parse tree extension without installing it:http://phpaspect.org/ast.
You can upload your own php script and get the xml tree or the tree visualization in png format.
I also put a mini documentation on a wiki page: http://phpaspect.org/wiki/doku.php?id=parse_tree.
If you have any question regarding parse_tree, you can ping the googlegroups associated to it:php_parse_tree@googlegroups.com.