CodeIgniter is a a community-developed open source PHP framework designed to simplify application development. Its goal is to enable you to develop projects much faster than you could if 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 lets you creatively focus on your project by minimizing the amount of code needed for a given task.
CodeIgniter 2.2.1 is the legacy version of the framework. For latest version of CodeIgniter, see the CodeIgniter 3.0 QuickStart.