I too came from a VB/PHP background and found libglade with C an easy enough transition. I have a tutorial on my website: http://www.micahcarrick.com/v2/content/view/28/20/
Learning C may be a far cry from VB, but it's syntax isn't that far from PHP. You have to do a little more work in C with memory, strings, and the like like but it "looks' similar to PHP. I didn't have too much trouble. Plus, the GTK+ "signals" are just like the VB "events" and the Glade Interface Designer is a lot like the VB IDE's interface designer.
That's my 2 cents.