Array Key Case Change

Using array_change_key_case function we can easily change case of array key.
Syntax: array array_change_key_case (array, $input);

Example: 
        $array_exp = array("my"=>1, "country"=>2);
        $output = array_change_key_case($array_exp,CASE_UPPER);
        print_r($output);

       Output: Array ( [MY] => 1 [COUNTRY] => 2 )

case either CASE_LOWER  or UPPER_CASE