htaccess mod rewrite - how to create virtual subdomains? - .htaccess

Question

I would like to create virtual subdomains through htaccess in the following way.
Entering:
http://testuser.domain.com/1/2/3/
Should be processed as:
http://www.domain.com/user.php?id=testuser&var1=1&var2=2&var3=3
HOWEVER, this rewrite should not use user.php, but index.php, in case someone enters:
http://www.domain.com or http://domain.com
This is what I got so far, however it doesn't seem to work.
Any help from a mod rewrite expert would be much appreciated.
Thanks in advance.
Options +FollowSymLinks
Options +Indexes
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{HTTP_HOST} ^(www\.)?domain.com$ [NC]
RewriteRule ^(.*)/?(.*)/?(.*)/?$ index.php?var1=$1&var2=$2&var3=$3 [NC,QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{HTTP_HOST} !^(www|mail).domain.com$ [NC]
RewriteCond %{HTTP_HOST} ^(www\.)?([a-z0-9-]+).domain.com$ [NC]
RewriteRule ^(.*)/?(.*)/?(.*)/?$ user.php?id=%2&var1=$1&var2=$2&var3=$3 [NC,QSA,L]

Answer 1

Your rules are actually very close to doing what you want them to. The only problem that I can see is in your test patterns for your two RewriteRule statements. Currently, you have
RewriteRule ^(.*)/?(.*)/?(.*)/?$ ...
...which happens to be equivalent to this:
RewriteRule ^(.*)$
This is because everything past the first capture group can match nothing and still be considered a match, so that first group is greedy and matches the whole input string without needing to defer to the other parts of the pattern.
Since the capture groups shouldn't capture forward slashes anyway, as they're being used as a variable delimiter here, the straightforward fix is to change them to [^/]*, as so:
Edit: I also modified the RewriteCond set in the second group to ignore the !-f condition in the case of /index.php, which will happen if you request the subdomain without anything after the domain.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{HTTP_HOST} ^(www\.)?domain.com$ [NC]
RewriteRule ^([^/]*)/?([^/]*)/?([^/]*)/?$ index.php?var1=$1&var2=$2&var3=$3 [NC,QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f [OR]
RewriteCond %{REQUEST_URI} ^/index.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{HTTP_HOST} !^(www|mail).domain.com$ [NC]
RewriteCond %{HTTP_HOST} ^(www\.)?([a-z0-9-]+).domain.com$ [NC]
RewriteRule ^([^/]*)/?([^/]*)/?([^/]*)/?$ user.php?id=%2&var1=$1&var2=$2&var3=$3 [NC,QSA,L]