Middleware in Leaf MVC

Middleware is a piece of code that runs before or after your application processes a request. It helps control the flow of requests and responses. For example, when a user visits a page on your app, you can use middleware can check if the user is logged in and if everything is okay, the request moves on to the next step; if not, the middleware can redirect the user.

Before you use middleware, Leaf has modules that offer a lot of functionality that you might not need to write your own middleware for. Be sure to check out the Leaf Modules page first to see if there's a module that already does what you need.

Creating Middleware

In Leaf MVC, middleware are just classes that extend the Leaf\Middleware class. Here's an example of a middleware that logs the request method and URI:

<?php

namespace App\Middleware;

use Leaf\Middleware;

class LogRequestMiddleware extends Middleware
{
    public function call()
    {
        $method = request()->method();
        $uri = request()->uri();

        echo "[$method] $uri\n";
    }
}

Of course, you don't have to do this manually. You can use the Aloe Console to generate a middleware for you:

php leaf g:middleware LogRequest

This will generate a LogRequestMiddleware.php file in the app/middleware folder.

Loading Middleware for all routes

All middleware generated using the Console will be automatically registered in the app/routes/index.php file. This file is automatically loaded by Leaf MVC, so any middleware you add to it will be loaded for every route in your application. If you don't want a middleware to be automatically loaded, you can remove it from the app/routes/index.php file.

use App\Middleware\LogRequestMiddleware;

...

/*
|--------------------------------------------------------------------------
| Set middleware for all routes
|--------------------------------------------------------------------------
|
| You can use app()->use() to load middleware for all
| routes in your application.
|
*/
app()->use(LogRequestMiddleware::class);
app()->use(AnotherMiddleware::class);

Loading Middleware for specific routes

If you don't want a middleware to be loaded for all routes in your application, you need to remove it from the app/middleware/Middleware.php file and load it manually in the route you want to use it in.

<?php

use App\Middleware\LogRequestMiddleware;

app()->get('/my-route', ['middleware' => LogRequestMiddleware::class, 'MyController@index']);

This will run the LogRequestMiddleware middleware only for the /my-route route.

Passing data from middleware

You can pass data from middleware to your route handler in order to use it in your controller or another middleware. You can do this using the response()->next() method.

<?php

namespace App\Middleware;

use Leaf\Middleware;

class LogRequestMiddleware extends Middleware
{
    public function call($next)
    {
        $method = request()->method();
        $uri = request()->uri();

        echo "[$method] $uri\n";

        response()->next('You can pass any value here');
    }
}

This uses Leaf's Response object to output data from the middleware that can only be accessed by your next handler (hence the name next). You can access that data in your route handler using the request()->next() method.

<?php

namespace App\Controllers;

class MyController extends Controller
{
    public function index()
    {
        $middlewareData = request()->next();

        echo $middlewareData; // will output "You can pass any value here"
    }
}

Once the data is read using request()->next(), it is removed from the request object and cannot be accessed again during the request lifecycle.