CodeIgniter is a powerful PHP framework with a very small footprint, built for developers who need a simple and elegant toolkit to create full-featured web applications.
Read User Guide Here
What’s inside the User Guide?
The User Guide contains an introduction, tutorial, a number of “how to” guides, and then reference documentation for the components that make up the framework.
Where else can I find the User Guide?
The user guide download is simply the zipped folder from the released version. It is included in the framework download.
Download User guide Here