Raffa was funded by Google during the Summer of Code. He implemented a PHP compiler for Mono and .NET. After a small pause, he has resumed work on his compiler and has now started a blog here:
Other .NET assemblies can now be accessed directly from within PHP scripts. Like that you can i.e. build GUIs with PHP using the Gnome libraries. I've already created two interesting examples including events and Drag&Drop features. You can import namespaces and types from other .NET assemblies with a spcial "using" syntax similar to the one known from C#. After doing so the imported types are avialable in the same way as classes implemented in PHP.