Intro to Middleware

What is Middleware?

Middleware is a software design pattern that enables seamless communication and data exchange between different systems, applications, or services. It plays a crucial role in facilitating interactions between disparate components, adding functionality, and enhancing overall system performance.

The Problem

In our previous project, we encountered an issue where a logged-in user was asked to register again when visiting the registration page. This was due to the lack of middleware implementation, which resulted in a poor user experience.

Middleware in PHP

In PHP, middleware can be used to handle user registration and login functionality, ensuring a smooth user experience. Middleware acts as a bridge between different components, enabling seamless communication and data exchange.

if ($_SESSION['user'] ?? false){ 
    header('location: /'); 
    exit(); 
}

It checks either the user is logged in or not. If not then exit the script to find authenticated user.

Route Configuration

In the routes.php file, we can add a 'guest' key to the route to associate it with the middleware:

$router->get('/register', 'controllers/registration/create.php')->only('guest');

Debugging the Only Method

To check if the project is working as expected, you can add a debug statement in the only method:

public function only($key){ 
    dd($key); 
}

It shows error as the only method cannot work with null value as it associated with get method and it doesn't return any value. So we have to rewrite the method.

Rewriting the Add Method

To return all values to the only method, we need to rewrite the add method in the router.php file as:

public function add($method, $uri, $controller) 
{ 
    $this->routes[] = [ 
        'uri' => $uri, 
        'controller' => $controller, 
        'method' => $method, 
        'middleware'=>null 
    ]; 
    return $this; 
}

Now we can see the project is working well.

Only Method

The only method in the router.php file needs to be modified to accept the middleware key:

public function only($key){ 
    $this->routes[array_key_last($this->routes)]['middleware']=$key; 
    return $this; 
}

Middleware Check

In the create.php file, we can check if the user is logged in or a guest using the middleware:

if ($route['middleware']==='guest'){ 
    if($_SESSION['user'] ?? false){ 
        header('location: /'); 
        exit(); 
    } 
} 
if ($route['middleware']==='auth'){ 
    if(! $_SESSION['user'] ?? false){ 
        header('location: /'); 
        exit(); 
    } 
}

Only authenticated user can have access to all pages while the guest can access the only limited pages.

Creating a Middleware Directory

To organize our middleware classes, create a new directory in the core folder named Middleware. As we have to make changes at one point for our relaxation, to save our efforts and time. By this we can make our project easier to understand. In this create 3 different classes.

Auth Middleware

The Authenticated.php file checks if the user is logged in and redirects to the home page if true:

<?php namespace Core\Middleware; 
class Authenticated { 
    public function handle() { 
        if (! $_SESSION['user'] ?? false) { 
            header('location: /'); 
            exit(); 
        } 
    } 
}

Guest Middleware

The Guest.php file checks if the user is not logged in and redirects to the home page if true:

<?php namespace Core\Middleware; 
class Guest { 
    public function handle() { 
        if ($_SESSION['user'] ?? false) { 
            header('location: /'); 
            exit(); 
        } 
    } 
}

Middleware Class

The Middleware.php file uses a MAP constant to map middleware keys to their respective classes. Also checks either the middleware exists or not. If not then show a uncaught exception to user to add middleware in project:

<?php namespace Core\Middleware; 
class Middleware { 
    public const MAP = [ 
        'guest' => Guest::class, 
        'auth' => Authenticated::class 
    ]; 
    public static function resolve($key) { 
        if (!$key) { 
            return; 
        } 
        $middleware = static::MAP[$key] ?? false; 
        if (!$middleware) { 
            throw new \Exception("No matching middleware found for key '{$key}'."); 
        } 
        (new $middleware)->handle(); 
    } 
}

Now we can see that by making these changes our project is working well.

I hope that you have clearly understood it.

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