<VirtualHost *:80>
...
<Location />
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /backend.php [L]
</IfModule>
DirectoryIndex backend.php
</Location>

</VirtualHost>