Global middleware in Laravel

Introduction

Global middleware runs on every request to your Laravel app. It helps you add common checks or actions for all users.

You want to check if the user is authenticated on every page.

You need to log every request made to your app.

You want to set a security header for all responses.

You want to handle CORS (Cross-Origin Resource Sharing) for all requests.

You want to trim all input data from forms automatically.

Syntax

Laravel

protected $middleware = [
    \App\Http\Middleware\CheckForMaintenanceMode::class,
    \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
    \App\Http\Middleware\TrimStrings::class,
    \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
];

This code goes inside the app/Http/Kernel.php file.

Each middleware class listed here runs on every HTTP request.

Examples

This example shows adding two middleware globally: one to trust proxies and one to check maintenance mode.

Laravel

protected $middleware = [
    \App\Http\Middleware\TrustProxies::class,
    \App\Http\Middleware\CheckForMaintenanceMode::class,
];

This example trims all input strings and converts empty strings to null for every request.

Laravel

protected $middleware = [
    \App\Http\Middleware\TrimStrings::class,
    \App\Http\Middleware\ConvertEmptyStringsToNull::class,
];

Sample Program

This middleware adds a custom header to every HTTP response. Adding it to the global middleware list makes it run on all requests.

Laravel

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class AddCustomHeader
{
    public function handle(Request $request, Closure $next)
    {
        $response = $next($request);
        $response->headers->set('X-Custom-Header', 'HelloWorld');
        return $response;
    }
}

// Then in app/Http/Kernel.php add:
// protected $middleware = [
//     \App\Http\Middleware\AddCustomHeader::class,
//     // other middleware...
// ];

Important Notes

Global middleware affects every request, so keep them efficient to avoid slowing your app.

You can still use route middleware for specific routes if you want to run middleware only sometimes.

Remember to register your custom middleware class in app/Http/Kernel.php under the $middleware array.

Summary

Global middleware runs on every request to your Laravel app.

It is defined in the $middleware array inside app/Http/Kernel.php.

Use it for tasks like authentication checks, logging, or modifying all responses.

Practice

1. What is the main purpose of global middleware in a Laravel application?

easy

A. To run code on every HTTP request to the application

B. To handle database migrations automatically

C. To define routes for the application

D. To manage user sessions only on login

Solution

1. Step 1: Understand what middleware does

   Middleware acts as a filter or layer that runs code before or after a request is handled.

2. Step 2: Identify the role of global middleware

   Global middleware runs on every HTTP request, applying tasks like authentication or logging universally.

3. Final Answer:

   To run code on every HTTP request to the application -> Option A

4. Quick Check:

   Global middleware = runs on every request [OK]

Hint: Global middleware affects all requests, not just some [OK]

Common Mistakes:

• Confusing middleware with routing
• Thinking middleware only runs on login
• Assuming middleware manages database

2. Which file in a Laravel project is used to register global middleware?

easy

A. config/app.php

B. routes/web.php

C. app/Http/Kernel.php

D. app/Providers/AppServiceProvider.php

Solution

1. Step 1: Recall where middleware is registered

   Middleware is registered in the Kernel class which manages HTTP middleware stacks.

2. Step 2: Identify the correct Kernel file

   In Laravel, the HTTP Kernel is located at app/Http/Kernel.php where global middleware is listed in the $middleware array.

3. Final Answer:

   app/Http/Kernel.php -> Option C

4. Quick Check:

   Global middleware registered in Kernel.php [OK]

Hint: Middleware registration is in Kernel.php, not routes or config [OK]

Common Mistakes:

• Choosing routes/web.php which defines routes only
• Confusing config/app.php with middleware registration
• Selecting service providers which are for services

3. Given this snippet in app/Http/Kernel.php:

$middleware = [
    \App\Http\Middleware\CheckAge::class,
];

What happens when a user sends a request to the app?

medium

A. The CheckAge middleware runs only on POST requests

B. The CheckAge middleware runs on every request

C. The CheckAge middleware runs only on routes with 'age' prefix

D. The CheckAge middleware does not run automatically

Solution

1. Step 1: Understand the $middleware array role

   The $middleware array in Kernel.php lists global middleware that runs on every request.

2. Step 2: Analyze the effect of adding CheckAge middleware there

   Since CheckAge is in $middleware, it will execute on all HTTP requests regardless of method or route.

3. Final Answer:

   The CheckAge middleware runs on every request -> Option B

4. Quick Check:

   $middleware = global middleware runs always [OK]

Hint: Middleware in $middleware runs on all requests, no exceptions [OK]

Common Mistakes:

• Thinking middleware runs only on certain HTTP methods
• Assuming middleware runs only on specific routes
• Believing middleware must be manually attached to routes

4. You added a new global middleware class to $middleware in app/Http/Kernel.php, but it does not run on requests. What is the most likely cause?

medium

A. The middleware class is registered in $routeMiddleware instead of $middleware

B. The middleware class is not imported in routes/web.php

C. The middleware class is missing a constructor

D. The middleware class does not implement the handle method

Solution

1. Step 1: Understand difference between $middleware and $routeMiddleware

   $middleware is for global middleware; $routeMiddleware is for middleware assigned to specific routes.

2. Step 2: Identify why middleware won't run globally

   If middleware is only registered in $routeMiddleware, it won't run on every request unless assigned to routes.

3. Final Answer:

   The middleware class is registered in $routeMiddleware instead of $middleware -> Option A

4. Quick Check:

   Global middleware must be in $middleware array [OK]

Hint: Global middleware must be in $middleware, not $routeMiddleware [OK]

Common Mistakes:

• Forgetting to implement handle method causes errors, not silent skip
• Importing middleware in routes/web.php is unnecessary
• Assuming constructor is required for middleware to run

5. You want to log every request's URL and method globally in your Laravel app. Which is the best way to do this using global middleware?

hard

A. Add logging code directly inside routes/web.php for each route

B. Register a route middleware and assign it to all routes manually

C. Use a controller constructor to log requests for each controller

D. Create a middleware with a handle method that logs request info and add it to $middleware in Kernel.php

Solution

1. Step 1: Identify how to apply logging globally

   Global middleware runs on every request, perfect for logging all requests centrally.

2. Step 2: Implement middleware and register globally

   Create middleware with a handle method that logs request URL and method, then add it to $middleware array in Kernel.php.

3. Step 3: Evaluate other options

   Logging in routes or controllers is repetitive and error-prone; assigning route middleware to all routes is inefficient.

4. Final Answer:

   Create a middleware with a handle method that logs request info and add it to $middleware in Kernel.php -> Option D

5. Quick Check:

   Global logging = global middleware in $middleware [OK]

Hint: Use global middleware for app-wide request logging [OK]

Common Mistakes:

• Logging inside routes causes duplication
• Controller constructors don't cover all requests
• Assigning route middleware manually is tedious and error-prone