It kind of depends on what you're looking for in an IDE. Phpmole might do it:
http://www.akbkhome.com/helpout/?rr=http%3A%2F%2Fwww.akbkhome.com%2FProjects%2FPhpmole-IDE%2F
But to understand why a drag & drop form painter goes against the underlying architecture of TK widgets you might want to read this:
http://www-hons.dcs.st-and.ac.uk/mirrors/gtkmm/tutorial-4.html
"Rather than making you specify the position and size of each widget in the window, you can instead tell GTK to arrange your widgets in rows, columns, and/or tables. GTK can size your window automatically, based on the sizes of the widgets it contains. You can further tune your layout by specifying padding distance, centering values, and minimum and maximum sizes for each of your widgets, among other things. GTK then uses all this information to do the right thing when the user resizes a window."
