Dynamic Subdomains in Apache

httpd.conf

RewriteEngine on
 # look for URLS like 'subdir.username.foo.bar'
 RewriteCond %{ENV:REDIRECT_STATUS} ^$
 RewriteCond %{HTTP_HOST} ([^.]+)\.([^.]+)\.foo\.bar$
 RewriteCond /home/%2/public_html/%1 -d
 RewriteRule ^(.+) %{HTTP_HOST}$1 [C]
 RewriteRule ([^.]+)\.([^.]+)\.foo\.bar(?::\d+)?(.*) /home/$2/public_html/$1$3 [L]
 
 # look for URLS liks 'username.foo.bar'
 RewriteCond %{ENV:REDIRECT_STATUS} ^$
 RewriteCond %{HTTP_HOST} ([^.]+)\.foo\.bar$
 RewriteCond /home/%1/public_html -d
 RewriteRule ^(.+) %{HTTP_HOST}$1 [C]
 RewriteRule ([^.]+)\.foo\.bar(?::\d+)?(.*) /home/$1/public_html$2 [L]

# On a server that doesn't have the userdir module and it's associated configs, we also need to add this:
 <Directory /home/*/public_html>
     AllowOverride FileInfo AuthConfig Limit Indexes
     Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec
     <Limit GET POST OPTIONS>
         Order allow,deny
         Allow from all
     </Limit>
     <LimitExcept GET POST OPTIONS>
         Order deny,allow
         Deny from all
     </LimitExcept>
 </Directory>

# Also, if the userdir module is enabled and you want to use PHP in userdirs,
# Ubuntu require the additional step of modifying /etc/apache2/mods-available/php5.conf:
<IfModule mod_php5.c>
     <FilesMatch "\.ph(p3?|tml)$">
         SetHandler application/x-httpd-php
     </FilesMatch>
     <FilesMatch "\.phps$">
         SetHandler application/x-httpd-php-source
     </FilesMatch>
     # To re-enable php in user directories comment the following lines
     # (from <IfModule ...> to </IfModule>.) Do NOT set it to On as it
     # prevents .htaccess files from disabling it.
    # <IfModule mod_userdir.c>
    #     <Directory /home/*/public_html>
    #          php_admin_value engine Off
    #     </Directory>
    # </IfModule>
 </IfModule>