A common question is does gd exist on my server so I can use in a PHP example. This script will help you out, upload it and then open in your browser to check whether GD exists.
<?php
if(!function_exists("gd_info"))
print "GD is not installed on this server";
if(function_exists("gd_info")) print "GD <b>is</b> installed on this server!";
?>
