Question

I have been reading a lot about how and why to use an MVC approach in an application. I have seen and understand examples of a Model, I have seen and understand examples of the View…. but I am STILL kind of fuzzy on the controller. I would really love to see a thorough enough example of a controller(s). (in PHP if possible, but any language will help)

Thank you.

PS: It would also be great if I could see an example of an index.php page, which decides which controller to use and how.

EDIT: I know what the job of the controller is, I just don’t really understand how to accomplish this in OOP.

Answer 1

Request example

Put something like this in your index.php:

<?php

// Holds data like $baseUrl etc.
include 'config.php';

$requestUrl = 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
$requestString = substr($requestUrl, strlen($baseUrl));

$urlParams = explode('/', $requestString);

// TODO: Consider security (see comments)
$controllerName = ucfirst(array_shift($urlParams)).'Controller';
$actionName = strtolower(array_shift($urlParams)).'Action';

// Here you should probably gather the rest as params

// Call the action
$controller = new $controllerName;
$controller->$actionName();

Really basic, but you get the idea… (I also didn’t take care of loading the controller class, but I guess that can be done either via autoloading or you know how to do it.)

Simple controller example (controllers/login.php):

<?php    

class LoginController
{
    function loginAction()
    {
        $username = $this->request->get('username');
        $password = $this->request->get('password');

        $this->loadModel('users');
        if ($this->users->validate($username, $password))
        {
            $userData = $this->users->fetch($username);
            AuthStorage::save($username, $userData);
            $this->redirect('secret_area');
        }
        else
        {
            $this->view->message = 'Invalid login';
            $this->view->render('error');
        }
    }

    function logoutAction()
    {
        if (AuthStorage::logged())
        {
            AuthStorage::remove();
            $this->redirect('index');
        }
        else
        {
            $this->view->message = 'You are not logged in.';
            $this->view->render('error');
        }
    }
}

As you see, the controller takes care of the “flow” of the application – the so-called application logic. It does not take care about data storage and presentation. It rather gathers all the necessary data (depending on the current request) and assigns it to the view…

Note that this would not work with any framework I know, but I’m sure you know what the functions are supposed to do.