Codeigniter Overview chapter discusses about the Features, Architectural Goals and Application Flow of CodeIgniter. CodeIgniter is an application framework which serves as a toolkit to build web applications more faster than PHP by providing rich set of libraries.

• CodeIgniter has free software licence namely Apache/BSD-style open source through which users can use with free of cost.
• It is light weight as the core system requires very small libraries and additional libraries can also be loaded dynamically upon user request.
• CodeIgniter is Fast.
• MVC is used here which separates logic and presentation.
• This generates clean and search-engine friendly URL’s which means the large URL links can be stored in a single variable and set of such variables are placed under codeigniter/application/config/routes.php file and URI routing (page landing) can be made clean and easy with that single variable mentioning in URL tab.
• CodeIgniter is thoroughly documented which serves as guide to developers.
• CodeIgniter can be extensible with use of our own libraries, helpers, hooks and classes.

Firstly the front controller namely index.php begins all the base resources like setting the type of website environment mode, setting application and system folder names that are needed to run the codeigniter. Once codeigniter started to run, the Routing process follows by calling the corresponding controller class methods and routes as a response to user actions within the web application. Thereafter URI routing, the user submitted input data will be validated, filtered, escaped for security purpose in order to prevent hacking of data. Then the secured data flows through the Application controller and this controller loads model, core libraries, helpers and returns back the output data to view for displaying in the browser.

M => Model : contains functions that helps to retrieve, insert and update information in the database. V => View : contains information which is going to be presented to user. C => Controller: serves as intermediary between Model and View and any other resources needed to process the HTTP request and generate webpages.

CodeIgniter is a dynamically instantiated, loosely coupled system with high component singularity which strives for simplicity, flexibility, and high performance.

To give a start to CodeIgniter, one should have basic knowledge of

• HTML
• Core and Advance PHP

Codeigniter Overview draws out following main points.

• CodeIgniter is light weight framework.
• It supports many features that are used for development of web applications.