We setup wildcard DNS like they explained above. So the a record is *.yourname.com
Then all of the subdomains are actually going to the same place, but PHP treats each subdomain as a different account.
We use the following code:
This code just sets the $account variable the same as the subdomain. You could then retrieve their files and other information based on their account.
This probably isn't as efficient as the ways they list above, but if you don't have access to BIND and/or limited .htaccess this method should work.
Hope this work!!