VirtualHost Alias detection in .htaccess

.htaccess

# VirtualHost Alias detection in .htaccess
# https://gist.github.com/2721888

<IfModule mod_rewrite.c>
    RewriteEngine On

    # Neat trick to rewrite with or without leading slash
    # Works by checking if DOCUMENT_ROOT + REQUEST_URI == REQUEST_FILENAME
    # If not, it is because you are in a virtual host alias and DOCUMENT_ROOT is not reliable
    # Example when alias is active:
    #   DOCUMENT_ROOT:      /var/www
    #   real root:          /var/www/example.com/
    #   REQUEST_FILENAME:   /var/www/example.com/foo
    #
    # Requesting via alias:
    #   full request:       http://example.com/foo
    #   REQUEST_URI:        /foo
    #   test:               /var/www + /foo == /var/www/example.com/foo  => false
    #   Rewrites to:        /app_dev.php
    #
    # Requesting via default host:
    #   full request:       http://localhost/example.com/foo
    #   REQUEST_URI:        /example.com/foo
    #   test:               /var/www + /example.com/foo == /var/www/example.com/foo  => true
    #   Rewrites to:        /example.com/app_dev.php

    <IfModule mod_vhost_alias.c>
      RewriteCond %{REQUEST_FILENAME} !-f
      RewriteCond %{REQUEST_FILENAME}:::%{DOCUMENT_ROOT}%{REQUEST_URI} ^(.+):::\1
      RewriteRule ^(.*)$ app_dev.php [QSA,L]

      RewriteCond %{REQUEST_FILENAME} !-f
      RewriteCond %{REQUEST_FILENAME}:::%{DOCUMENT_ROOT}%{REQUEST_URI} !^(.+):::\1
      RewriteRule ^(.*)$ /app_dev.php [QSA,L]
    </IfModule>

    # All this is useless if mod_vhost_alias is not active
    <IfModule !mod_vhost_alias.c>
      RewriteCond %{REQUEST_FILENAME} !-f
      RewriteRule ^(.*)$ app_dev.php [QSA,L]
    </IfModule>

    # While the method above is nice, it is slow
    # Be sure to deactivate all this when deploying, with or without RewriteBase

    ## RewriteBase /
    #  RewriteCond %{REQUEST_FILENAME} !-f
    #  RewriteRule ^(.*)$ app.php [QSA,L]
</IfModule>