okay, you have that backwards. it is suppose to be the seperator and then the string; you have the string and then the seperator.
array[] = explode("/".$url);
also, i would echo out that url just incase it is null. you never know, right. here is the url to the explode function from php.net
http://us3.php.net/manual/en/function.explode.php
good luck,
bako