你用什么作为app应用的后台服务？

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/

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