Description:
------------
Some Datastructures like SplFixedArray and SplObjectStorage could have a sort method where we can pass an optional callback and it sorts the original object or even return a new one.

Test script:
---------------
<?php
$array = new SplFixedArray(10);
for ($i = 0; $i < 10; $i++) {
    $array[$i] = mt_rand(1, 10);
};

$array->sort();
$array->sort(function ($a, $b) { return $b - $a; });
/**
 * Or:
 * $newArray = $array->sort();
 */

Expected result:
----------------
A sorted SPL Datastructure

Actual result:
--------------
FATAL ERROR Uncaught Error: Call to undefined method SplFixedArray::sort()