note 51147 modified in function.shuffle by danbrown

[EDIT by danbrown AT php DOT net: As pointed out on 25 July, 2008, by "Anonymous", this implementation may have some errors or inconsistencies that may cause this function not to achieve the desired result. "Anonymous" provided the following link for more information: http://en.wikipedia.org/wiki/Fisher-Yates_shuffle] This is an attempt to get the Fisher Yates shuffle right, and as optimized as possible. The array items are stepped through from last to first, each being swapped with another between itself and the beginning of the array (N-1 shuffles required.) Using list() to swap array vars instead of a tmp var proved to be slightly slower. Testing for $i = $j decreases performance as the array size increases, so it was left out (elements are always swapped.) <?php function fisherYatesShuffle(&$items) { for ($i = count($items) - 1; $i > 0; $i--) { $j = @mt_rand(0, $i); $tmp = $items[$i]; $items[$i] = $items[$j]; $items[$j] = $tmp; } } ?> --was-- This is an attempt to get the Fisher Yates shuffle right, and as optimized as possible. The array items are stepped through from last to first, each being swapped with another between itself and the beginning of the array (N-1 shuffles required.) Using list() to swap array vars instead of a tmp var proved to be slightly slower. Testing for $i = $j decreases performance as the array size increases, so it was left out (elements are always swapped.) function fisherYatesShuffle(&$items) { for ($i = count($items) - 1; $i > 0; $i--) { $j = @mt_rand(0, $i); $tmp = $items[$i]; $items[$i] = $items[$j]; $items[$j] = $tmp; } } http://php.net/manual/en/function.shuffle.php