Trying to create a scrambling script but got into a problem...

[soft2050]

Using Regular Expression is not a good choice to do that. You could use str_shuffle to scramble a string
http://php.net/manual/en/function.str-shuffle.php

<?php
$key = $_SERVER['QUERY_STRING'];
$result = str_shuffle($key);
echo "Original:<br/>";
echo $key."<br/>";
echo "Scrambled:<br/>";
echo $result;
?>