Creating callbacks to a php function from a module?

Would it be possible with the current state of the zend-engine to allow for a module to create a callback to a function in an actual php-script? The reason I'm asking is because I would love to see php beeing able to use GUI bindings for qt,gtk,tk or whatever. As it is now I have to resort to using Python for doing that kind of things that need a GUI, but I really do prefer the syntax and language of php. If this really was possible I wouldn't hesitate to start smashing together some module that in time would allow for use of GTK or QT.