Shell exec is a PHP function through which you can execute shell commands. I think the Shell is a part of the OS. So if you have shell access, You can do a lot with it. That's why it's disabled Even if it were possible to use byethost for PHP and helihost for everything else, Byethost ToS probably require you to have a website with a whole website that gets a few hits. They won't like you using them just for a few scripts.