CodeIgniter is based on the popular MVC development pattern. While controller classes are a compulsory part of development in CodeIgniter. Models and views are optional in CI. CodeIgniter can be also modified to use Hierarchical Model View Controller (HMVC[4]) which allows developers to maintain modular grouping of Controller, Models and View arranged in a sub-directory format.
CodeIgniter is a Framework for developers who build web applications using PHP. CodeIgniter has a goal to enable you to develop projects faster than you were writing code from scratch, by providing a rich set of libraries for commonly needed tasks, as well as a simple interface and logical structure to access these libraries. CodeIgniter is a very fast framework and best for development. It really has better performance than other frameworks.