note 54924 added to function.shuffle

Benton, Justin: Your updated Fisher-Yates implementations with forward traversal order miss a rather important point; in changing the order of traversal, you must also change the range of the array from which you select the element with which to swap element i. Fisher-Yates partitions the initial data set into a 'shuffled' and 'unshuffled' region, selecting randomly from the 'unshuffled' set to build a shuffled set. To maintain this, you should assign $j = mt_rand($i, count($items-1)). (Assuming 'count' is the appropriate idiom in PHP. I'm not a PHP person). You'll then doubtless want to pull the 'count' call outside the loop, too. Note that the random range *includes* $i. If it didn't, it'd be impossible for an element to appear in the same position in the output as it appeared in the input, making a two-element array 'shuffle' deterministic. With the code, as written drawing from the random range [0, $i], the shuffle will exhibit a bias for elements appearing early in the input array to remain early in the output. ---- Manual Page -- http://www.php.net/manual/en/function.shuffle.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+54924 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+54924&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+54924&report=yes Search -- http://master.php.net/manage/user-notes.php