sending a response back to a PHP site from rails application

   I have an existing php application running commercially..Now I have a
new rails application..So I have three fields like user_name ,password
and company in the php page .Which when submitting connecting to my
rails application ..To elaborate
suppose I enter

username= user1
password = pass1
company = company1

    Then when submitting the php page it should goes to my rails
application on port 3000 This I could do..Similary if I give a different
company name then it wii be connected to my rails application on port

       Now my request is if anything error happens for wrong password or
wrong company name (for example) I need to redirect from rails
controller action to the php login page it self..This I dont know how to
do...I am totally new to this type of interconnecting two
platforms...Could you please help me to solve this problem

Thanks in advance

you must have some kind of authentication system in Rails app.

so after comparing posted values..

if user exists then redirect_to "home/index" [home is controller and
index action for rails app]
redirect_to ""

let me know