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 writing custom middleware, check out Leaf Modules—they offer built-in functionality that might already cover your needs, saving you time and effort.

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 MVC 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

Once you generate your middleware, you can choose to load it for all routes in your application. This means that the middleware will run for every request made to your application, regardless of the route. It could be useful for logging requests, checking if a user is authenticated, etc.

To do this, you need to add the middleware to the app/routes/index.php file. We have added an example middleware to the file for you:

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

The most common use case for middleware is to load it for specific routes, instead of all routes. You can do this by adding the middleware to the particular route you want to use it in using route parameters.

<?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 using response()->next(), making it available in your controller or another middleware.

<?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');  
    }
}

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"
    }
}

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

What to read next

Middleware is a powerful tool that can help you control the flow of requests in your application, but Leaf already has a lot of functionality built-in that you might not need to write your own middleware for. Check out some of the other features of Leaf & Leaf MVC:

• Authentication

  Learn more about routing in Leaf MVC, dynamic routes, middleware and more.
• Roles & Permissions

  Learn how to process incoming requests, handle form submissions, and more.
• Session Data

  Save user data, flash messages, and more using Leaf's session module.
• Frontend

  Learn about SSR, SPA, and how to use Leaf with your favorite frontend framework.