Hi 
Just a head up, that you should really use strict comparison in your PHP everywhere. This includes the usual === instead of == and !== instead of !=. But also a bunch of PHP functions, do not per default do strict comparison. This includes in_array, array_search and array_keys. This functions have a third parameter $strict which needs to be manually set to true.
This can save you from some unexpected behavior which is hard to debug
Cheers and happy hacking