I’ve just updated my Symfony 2 implementation of TodoMVC using Backbone.js and Chaplin.js for the UI.
It is now compatible with Symfony 2.3 (the current version and first LTS of Symfony 2). I’ve moved the decoder which converts JSON data to application/x-www-form-urlencoded directly in FOSRest.
Take a look at this bundle if you want to use Backbone and Chaplin with Symfony. The demo is still online.