Bug #67233 [Opn->Dup]: 5.5.12 array rand is not random

Edit report at https://bugs.php.net/bug.php?id=67233&edit=1 ID: 67233 Updated by: levim@php.net Reported by: bugsphp077 at nabialek dot org Summary: 5.5.12 array rand is not random -Status: Open +Status: Duplicate Type: Bug Package: Arrays related Operating System: Windows 8.1 PHP Version: 5.5.12 Block user comment: N Private report: N New Comment: This is well known, but sadly undocumented. Here's a bug report from 2001: https://bugs.php.net/bug.php?id=12312 It also appears to be more severe on Windows: https://bugs.php.net/bug.php?id=45301 I'm closing this as a duplicate of the latter bug. Previous Comments: ------------------------------------------------------------------------ [2014-05-08 09:05:01] bugsphp077 at nabialek dot org Description: ------------ --- From manual page: http://www.php.net/function.array-rand --- Function array_rand does not choose random value. In documentation there is info that there's no need to use srand or mt_srand any more. In fact using srand function before launching randTest function (in test script) solve this issue. However using mt_srand function (both with and without seed) doesn't solve this issue Test script: --------------- <?php $letters = array('a','b','c','d','e','f','g','h'); $array = array(); // mt_rand used just for filling array, it may be filled manually if neccessary for ($i=0; $i< 200; ++$i) { $array[] = $letters[mt_rand(0,count($letters)-1)]; } for ($i=0; $i< 10000; ++$i) { echo randTest($array)."<br />"; } function randTest($array) { $out = array(); while (count($array) > 0) { $index = array_rand($array,1); $out[] = $array[$index]; unset($array[$index]); } return implode('', $out); } Expected result: ---------------- All lines should be random or at least no visible pattern of repetition should be possible to find Actual result: -------------- It repeats its results in test script each 14 times. I mean in output line 1 is the same as line 14, line 2 is the same as line 15, line 3 is the same as line 16 so it means it is not random at all. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=67233&edit=1