I'm going to debunk another myth that might keep you from trying out Ruby on Rails (or any other new server language). MYTH: Once you start using Rails, you have to do everything in Rails.
I wanted to integrate a forum into my new Rails site. So I took a look at the Rails forums out there and found a whopping three: Beast, RForum and Opinion. Unfortunately, they all suck. Ok, to be fair, they're all rather new, and are still in development. But they still suck.
At first, I was okay with using a crappy forum. But I didn't just need a standalone forum — I needed to totally integrate the forum into my existing site, users and all. But rails apps want to run on their own server. I don't know why, they're all claustrophobic or something. When you try to get two of them to share a server, one tends to peck the other's eyes out like it's a rails-powered cockfight.
So after way too much time spent cleaning up feathers and blood, I decided to give one of the classic PHP forums a chance. I decided Vanilla was going to be my forum of choice, and I got to work.
It turned out that it took me less time to integrate Vanilla with my Rails app than all the time I spent recoding routes.rb to make Beast work. Here's some tips to get a PHP app to coexist with rails:
PHP apps are very happy to live inside a subdirectory inside another site. They love it. So what better place to drop one than inside a rails app's public directory. (Try doing that with a rails forum).
This also has the benefit of having a single domain, which makes sharing cookies slightly easier.
This isn't a requirement, but it just simplifies things slightly. Vanilla uses a table naming convention like LMU_*, and I'm sure most other (non-rails) forums do the same, so the two can coexist fairly easily. This way you can do stuff like joins across your own tables and the forum tables.
Rather than share a single 'users' table (which is pretty much the only way you'd be able to get two rails apps to coexist in a single database), just add rows to the forum's user table every time a user signs up on your rails app. And of course, don't forget to use a foreign key to relate the two.
Vanilla makes a single sign-on feature easy through a "Remember me" feature. Basically, if 2 cookies are set ('lussumocookieone' for the UserID, and 'lussumocookietwo' for the VerificationKey by default), then the user is automatically logged in. So all you have to do is look up (or write) the VerificationKey in LMU_Users and set these cookies whenever a user logs in to your rails app.
This is a really easy hack. Just erase the 'PHPSESSID' and '_session_id' cookies, and the user will be logged out from the forum. This way you can have a single sign-out too.
Okay, this post got pretty specific. But the lessons can be applied to the coexistence of any server-side apps. Communicate via the database and cookies, and you can pretty much do anything.