Really like this. Simpler than searching PHP documentation if only needing to know something quickly. Nice idea :)
I wouldn't have clicked it until looking for a back button. Might be worth leaving it as text, and maybe placing a back button to the left of it? Personally I think something similar to the back button in Windows Phone would look nice. Something like the button here: http://i.msdn.microsoft.com/dynimg/IC505392.png