CodeIgniter Application Architecture

The following picture depicts the codeigniter application architecture or request flow for any client request that comes to it –

index.php:- The index.php works as the application front controller, that initializes or load the base resources required for application.

Router:- The Router examines the incoming request and decide what should be done next, whether to pass this request to caching or to pass it to security.

Caching:- If a cache file exists corresponding to incoming request, it is sent directly to the browser, ignoring the further processing.

Security:- Before request is routed to application controller, the request and submitted data is examined for security check.

Application Controller:- The Application Controller loads all of the required Models, Libraries, Helpers, Plugins, Scripts and any other resources required for processing the specific request.

View:- The finalized output is incorporated into View is sent to the web browser. If View is not cached then it will be cached first for subsequent requests.