Earl Boykins in college WAS 5'7''...because inches were ADDED. Now, he's 5'5'' in the NBA, because that's a great marketing story. Shortest guy in the league. If you think about it, 5'5'' seems TONS smaller than 5'7'' in the NBA.
As for Barkley, I would say he's 6'5''...regardless of the mug shot, simply because in my first ever mugshot, the top of MY head was at 5'3''...when I'm 5'6''. If I ever get a scanner, I'll show it to you guys.
Either way, he was a GREAT rebounder, and it had NOTHING to do with his height. PERIOD.