mt_shuffle.php

<?php
/**
 * Shuffles an array using mt_rand() instead of rand().
 * CAUTION: Unlike shuffle(), returns a new array, leaving the source untouched. It's better that way.
 * CAUTION: Won't work with associative arrays. Who would shuffle an associative array anyways?
 * 
 * @param array $deck The index-based array to be shuffled.
 * @return array A new array containing exactly the same elements in a random order.
 * 
 * @see http://stackoverflow.com/questions/5694319/how-random-is-phps-shuffle-function
 * @see https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
 */

function mt_shuffle($deck) {
  for ($i = count($deck)-1; $i >= 1; $i--) {
    $j = mt_rand(0, $i);
    list($deck[$j], $deck[$i]) = array($deck[$i], $deck[$j]);
  }
  return $deck;
}
?>