note 100236 deleted from function.rand by danbrown
| From: | danbrown@php.net | Date: | Sun, 03 Oct 2010 22:16:34 +0000 |
| Subject: | note 100236 deleted from function.rand by danbrown | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-172917@lists.php.net to get a copy of this message | ||
Note Submitter: charlie at brown dot org
----
random dot org/analysis/ has a side-by-side graphic of a true random number generator and PHP's
(pseudo-random) rand(). It shows strong vertical patterns(bad). I did my own to see how bad it is
but I can't reproduce their results. Here's my code. It looks as good as their true random
graphic:
<?php
define('WIDTH', 512);
define('HEIGHT', WIDTH);
$gd = imagecreatetruecolor(WIDTH, HEIGHT);
$white = imagecolorallocate($gd, 255, 255, 255);
for($col=0; $col<WIDTH; $col++) {
for($row=0; $row<HEIGHT; $row++) {
$r = (int)rand(0,1);
if($r) {
imagesetpixel($gd, $col, $row, $white);
}
}
}
header('Content-Type: image/png');
imagepng($gd);
?>
I tested on a linux server so maybe it's just PHP in Windows that has a problem.