Configuring Apache to accept wilcard domains can be very useful. Having the wildcard domain go to a specific subdomain is even more so, so here's a short how to.

Step one is to set up your domain to accept wildcard domains. This is done by configuring the A record for your domain so that any hits to anything.yourdomain.com (and by anything, I mean *.yourdomain.com) go to the IP address you have assigned to your server. Permalink for this article http://mirror.magicode.org/content/Configuring_wildcard_subdomains_with_Apache

Step two is to configure Apache to accept *.yourdomain.com. This is typically done by editing httpd.conf like so:

1. # this accepts any subdomain
3. DocumentRoot /www/yourdomain
4. ServerName www.yourdomain.com
5. ServerAlias *.yourdomain.com

That's the easy part, and if all you want is point example.yourdomain.com to www.yourdomain.com (or any other subdomain to www.yourdomain.com for that matter), you're done.

If you want to take it a step further, so that example.yourdomain.com points to www.yourdomain.com/example, you need to use Apache's Rewrite engine. It's a tricky beast, but let's give it a go.

Here's how you do it:

1. #Turn the RewriteEngine on.
2. RewriteEngine On
4. #Fetch the subdomain. This accepts any combination of words
5. RewriteCond %{HTTP_HOST} ^([-a-z0-9]+)\.yourdomain.com$
7. #Make sure the subdomain is not www, which we want to leave
8. #alone. If you have more subdomains to exclude, use a pipe
9. #(|) to separate them -- like www|mail|etc...
10. RewriteCond %{1} !^(www)$
12. #Verify that the directory exists before we rewrite
13. RewriteCond /web/yourdomain/public_html/%1 -d
15. #Finally, stop this from looping, which would kill
16. #the user experience in five parsecs (joke)
17. RewriteCond %{REQUEST_FILENAME} !^/web/yourdomain/public_html/
19. #And finally, the rewrite
20. RewriteRule (.*) /web/yourdomain/public_html/%1/$1

All you have to do now is store the above in the file called .htaccess in the root of your public folder (or add it to the VirtualHost directive in httpd.conf) :).