Phusion passenger + php

Hello , I excuse me if this is a bit offtopic.

I have an application running with phusion passenger and It’s working
fine for the moment.

The problem is that I need to run a php application (phpbb) on the same
domain and I’m having problems to get it working.

The problem is that the forum url (mydomain.com/forum) is served by
rails, I get a 404 error from my rails application.

However if I use my domain ip instead of the domain name the php
application is served and works correctly.

My apache config directive for the domain is like this:

<VirtualHost *>
ServerName www.mydomain.com
DocumentRoot /home/user/public_html/mydomain/public

I hope you can help me with this.
Thanks for reading.
ALfredo