the problem that PHP doesn't have is configuring the environment to run it. You just install a few pkgs and boom!
Even plugins come in php itself and aren't seperately pkged. There's no gems, no seperate server to serve the ruby backend. Just upload/push your code and it'll run. And any cheap host would do it. The _only_ advantage I see here is that I can increase my resources for the app (if it's like heroku) just with the click of a button without restarting the server.
But I can't wait to be proved wrong. All the best guys :)