Problem: You have a symfony project with 2 applications ‘customers’ and ‘resellers’. You want www.myretail.com to use ‘customer’ application and www.myresellers.com to use ‘resellers’ application.

here customers app is your default ‘frontend’ app with index.php and resellers app has say ‘reseller.php’ and ‘reseller_dev.php’ controller files.

Solution:
Separate the web folder for each domain you want handle.

so customers content is in /project/web folder and resellers content is in /project/web-reseller/ folder. Move your reseller.php to web-reseller folder and rename it to index.php

You will need to create two virtual host for each domain with document root pointing to their respective folders.

Another solution is to have different .htaccess files. In case you do not want to create separate web folder you can create another .htaccess_reseller file in the web/ folder and redirect all request to reseller.php instead of index.php