In brief, Winbinder is a GUI toolkit for PHP and Windows. The main site seems to be down right now but the code is available @http://sourceforge.net/projects/winbinder/. Compared to PHP-GTK it’s Windows only but at the same time fast and gives you the Windows look and feel. Winbinder also seems more suited to PHP hackers (procedural rather than OO)
All that said, would still say that Python plus wxPython is the sane option if you want a dynamic language to build GUIs in – mature, cross platform, native look and feel etc. The easiest way to express that is simply to link to applications like taskcoach or ActiveGrid’s Application Builder (which is in fact pretty amazing).