What is CodeIgniter?

CodeIgniter is a PHP MVC framework used to develop web applications quickly. CodeIgniter provides out-of-the-box libraries to connect to the database and perform various operations such as sending emails, uploading files, managing sessions, etc.

The PHP CodeIgniter framework uses the Model-View-Controller architectural design. 

How CodeIgniter Works?

CodeIgniter is an MVC framework. MVC stands for Model View Controller. When a user requests a resource, the controller responds first. The controller understands the user's request and then requests the necessary data.