(PHP 4 >= 4.0.5)array_search -- Searches the array for a given value and returns the corresponding key if successful
Searches haystack for needle and returns the key if it is found in the array, FALSE otherwise.
Note: Prior to PHP 4.2.0, array_search() returns NULL on failure instead of FALSE.
If the optional third parameter strict is set to TRUE then the array_search() will also check the types of the needle in the haystack.
This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.