Ruby on Rails还是PHP?
PHP+Mysql作为Android app的后台:http://www.tutorialspoint.com/android/android_php_mysql.htm
PHP+Mysql作为IOS app的web service后台:
http://www.raywenderlich.com/2941/how-to-write-a-simple-phpmysql-web-service-for-an-ios-app
http://php.about.com/od/learnmysql/fl/Using-MySQL-with-iOS.htm
Ruby on Rails作为app的后台:
https://matteomelani.wordpress.com/2011/10/17/authentication-for-mobile-devices/
http://collectiveidea.com/blog/archives/2013/06/13/building-awesome-rails-apis-part-1/
http://railscasts.com/episodes/350-rest-api-versioning
你也可以用开源的BaaS项目作为后台:
Baasbox:
http://www.baasbox.com/features/
https://github.com/baasbox/baasbox
DreamFactory:
https://www.dreamfactory.com/features
https://github.com/dreamfactorysoftware/dreamfactory
国外有一些专门做BaaS(Backend as a Service)的公司或者项目,可以参考:
http://www.raywenderlich.com/20482/how-to-choose-the-best-backend-provider-for-your-ios-app-parse-vs-stackmob-vs-appcelerator-cloud-and-more
http://nordicapis.com/why-you-should-build-apps-with-an-api-backend-baas/