How to change array keys from uppercase to lowercase?

The array_change_key_case() function changes all keys in an array to lowercase or uppercase.

Syntax:

array_change_key_case(array,case);
array - The array to work on 
CASE_LOWER - Default value. Changes the keys to lowercase
CASE_UPPER - Changes the keys to uppercase

This function takes array as a first parameter, It will return FALSE if given input is not an array.
Second parameter is optional,you can pass either CASE_LOWER or CASE_UPPER and default value is “CASE_LOWER”. This function is supported from PHP 4.2 and above.

Example :

 1, "SecOnd" => 4);
print_r(array_change_key_case($input_array, CASE_UPPER));
?>
// output :
Array
(
    [FIRST] => 1
    [SECOND] => 4
)

Example :

 1, "SecOnd" => 4);
print_r(array_change_key_case($input_array));
?>
// output :
Array
(
    [first] => 1
    [second] => 4
)