If needle is a string, the comparison is done in a case-sensitive manner.
If the third parameter strict is set to TRUE then the array_search() function will search for identical elements in the haystack. This means it will also check the types of theneedle in the haystack, and objects must be the same instance.
Returns the key for needle if it is found in the array, FALSE otherwise.
If needle is found in haystack more than once, the first matching key is returned. To return the keys for all matching values, use array_keys() with the optional search_value parameter instead.
This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.
As with all internal PHP functions as of 5.3.0, array_search() returns NULL if invalid parameters are passed to it.
Prior to PHP 4.2.0, array_search() returns NULL on failure instead of FALSE.