如何重新排序多维数组？

How to sort the array alphabetically below using as the key criterion label? I tried using array_multisort, usort, rsort, and sort, but it did not work.

array(3) {
  [0]=>
  array(2) {
    ["id"]=>
    string(1) "9"
    ["label"]=>
    string(26) "ffffff"
  }
  [1]=>
  array(2) {
    ["id"]=>
    string(2) "10"
    ["label"]=>
    string(25) "aaaaaaaaa"
  }
  [2]=>
  array(2) {
    ["id"]=>
    string(1) "6"
    ["label"]=>
    string(5) "dddddd"
  }
}

You can sort the array using both usort() and strcmp()

usort($arr, function($e1, $e2)
{
    $cmp = strcmp($e1['label'], $e2['label']);
    if($cmp == 0) { return 0; }
    return $cmp > 0 ? 1 : -1;
});