The MVC framework is a widely used and very effective way of organizing a complex website. CI uses it to help you sort out your own code, but it is also fairly flexible about how it does so.

Try to keep in mind the two principles of 'loose coupling' and 'component singularity' when you write your own code. Don't worry too much whether your application conforms to the strict theory of MVC or not. The crucial thing is to understand what the different types of file are, and how they relate to each other. Then, you can decide whether to write your own code in library or model files, or as helpers or plug-ins.

We've looked at the CI file structure, and seen how you can, if you want, inspect all the CI code, but (thankfully!) you don't have to.

We did tinker with one of the original files: the config file, which holds critical site information in one place to make it easier for us to upgrade or change later on.

We've seen the basic object structure of a controller, and used a simple constructor...