array_change_key_case

Description

array_change_key_case() changes the keys in the input array to be all lowercase or uppercase. The change depends on the last optional case parameter. You can pass two constants there, CASE_UPPER and CASE_LOWER. The default is CASE_LOWER. The function will leave number indices as is.

<?php
$input_array = array("FirSt" => 1, "SecOnd" => 4);
print_r(array_change_key_case($input_array, CASE_UPPER));
 ?>

Array
(
    [FIRST] => 1
    [SECOND] => 4
 )

If an array has indices that will be the same once run through this function (e.g. "keY" and "kEY"), the value that is later in the array will override other indices.