How to route a form post to PHP file from Rails?

I already have a php file that takes the contents of an html form that I've now converted to Rails. I don't want to rewrite the php in rails but I'm having issues posting to it. I put开发者_开发百科 the php file in the public directory and can access it if I type the address directly but when I submit a form with it as the action rails serves a 404 not found. How do I tell Rails to serve it from apache?