copy this to a txt file and rename gallery.php
PHP Code:
<?php
$fileName = "./gallerylist.txt";
mt_srand( (double) microtime() * 1000000 );
$a = file($fileName);
$randNum = mt_rand( 0, sizeof($a)-1 );
header( "Location: ". $a[$randNum] );
?>
now make a gallerylist.txt file and put 1 gallery url per line
now point your link to
http://www.url.com/gallery.php
have a nice fucking day
