In this series we're going to build a web billboard application from scratch, we're going to use CodeIgniter to handle the back-end service and BackboneJS for the web client. In the first two parts of the series we'll create the back-end service and then the client application in the last two.
They walk you through the steps to to set up a MongoDB to handle the data for the backend and configuring CodeIgniter to work with it. He helps you get it set up to handle REST requests from the BackboneJS frontend too (including OPTIONS handling). He shows how to parse the input and handle the output as well as models to connect to the database resources and how to handle sessions.