you could always try a rewrite rule
RewriteRule
http://(.*).yoururl.com http://www.yoururl.com/username=$1
just set your httpd.conf file as so (if it is your server, if not, your host can most likely set it up for you):
<VirtualHost *:80>
DocumentRoot "/path/to/www/"
ServerName *.yoururl.com
</VirtualHost>
dont hold me to it though, I have not messed around with Apache in a while, so I am bound to be a bit rusty.
If it does work, it will actually just see your "subdomain" as the php get variable username, in which case, you can just ignore www. Otherwise, you can always stick with the following (which I know works like a charm):
RewriteRule yoururl.com/(.*) yoururl.com/user.php?username=$1
dont forget RewriteEngine on and Options +FollowSymLinks though!
__________________
Jason Corradino
Applications Developer, Interactive Support - Tribune Technology
J2EE Development, Script Tinkering - Develop, Support, and Maintain
Tribune websites.