The PHP-GTK is ported for Win32 (and has been since release 0.0.1 back in April). The Win32 port does tend to lag behind *Nix on the official releases, but that's only by a couple days. Of course, the real fun is in the CVS tree, but that's another story🙂 Getting a CVS copy of PHP-GTK to work on Win32 is just as tricky, if not more so, than getting a functional CVS version of PHP itself.
The majority of the GTK core widget set has been implemented in the bind and is available on both *Nix and Win32. There are some 3rd party widgets, Scintilla and GtkHTML for example, which aren't currently supported on Win32... but libGlade is now supported in the most recent release. So you can now design all your interface layouts using XML stylesheets if you choose.
Some of the current limitations of the Win32 port are actaully related to issues in the port of GTK itself to Win32. Needless to say, Andrei et. al. are going to leave that mess to the folks over at GTK🙂 However, there are some plans to move to GTK 2.0 as soon as it's stable (PHP-GTK currently uses GTK 1.2.6).
-geff