Registering middleware in Laravel

Introduction

Middleware helps control what happens before or after a web request. Registering middleware tells Laravel to use it in your app.

You want to check if a user is logged in before showing a page.

You need to log every request to your app.

You want to block certain IP addresses from accessing your site.

You want to add headers to all responses for security.

You want to run code after a request finishes, like clearing cache.

Syntax

Laravel

protected $routeMiddleware = [
    'name' => '\App\Http\Middleware\YourMiddleware',
];

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

The key 'name' is how you refer to the middleware in routes.

Examples

This registers the built-in authentication middleware with the name 'auth'.

Laravel

protected $routeMiddleware = [
    'auth' => '\App\Http\Middleware\Authenticate',
];

This registers a custom middleware named 'checkAge' that you created.

Laravel

protected $routeMiddleware = [
    'checkAge' => '\App\Http\Middleware\CheckAge',
];

This adds middleware to a group called 'web' so all routes in that group use them.

Laravel

protected $middlewareGroups = [
    'web' => [
        '\App\Http\Middleware\EncryptCookies',
        'auth',
    ],
];

Sample Program

This example shows how to register two middleware in the Kernel and then use them on routes. The 'auth' middleware protects the '/profile' page, and the custom 'checkAge' middleware protects '/restricted'.

Laravel

<?php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    protected $routeMiddleware = [
        'auth' => \App\Http\Middleware\Authenticate::class,
        'checkAge' => \App\Http\Middleware\CheckAge::class,
    ];
}

// In routes/web.php

use Illuminate\Support\Facades\Route;

Route::middleware('auth')->get('/profile', function () {
    return 'User Profile Page';
});

Route::middleware('checkAge')->get('/restricted', function () {
    return 'Restricted Content';
});

Important Notes

Always register your middleware in app/Http/Kernel.php to use it in routes.

You can register middleware globally or for specific routes.

Use meaningful names for middleware keys to keep your code clear.

Summary

Middleware controls request handling in Laravel.

Register middleware in Kernel.php to use it.

Apply middleware to routes by their registered name.

Practice

1. What is the main purpose of registering middleware in Laravel's Kernel.php file?

easy

A. To define database connections

B. To make middleware available for use in routes and controllers

C. To create new views

D. To register event listeners

Solution

1. Step 1: Understand middleware role

   Middleware acts as a filter for HTTP requests in Laravel.

2. Step 2: Purpose of registering middleware

   Registering middleware in Kernel.php makes it available to assign to routes or groups.

3. Final Answer:

   To make middleware available for use in routes and controllers -> Option B

4. Quick Check:

   Middleware registration = availability for routes [OK]

Hint: Middleware must be registered to use it in routes [OK]

Common Mistakes:

• Confusing middleware registration with database setup
• Thinking middleware creates views
• Mixing middleware with event listeners

2. Which of the following is the correct way to register a route middleware named checkAge in app/Http/Kernel.php?

easy

A. 'checkAge' => \App\Http\Middleware\CheckAge::class,

B. 'checkAge' => 'CheckAgeMiddleware',

C. 'checkAge' => new CheckAge(),

D. 'checkAge' => 'middleware.checkAge',

Solution

1. Step 1: Locate middleware registration syntax

   In Kernel.php, route middleware are registered as key-value pairs with the key as the name and value as the class reference.

2. Step 2: Match correct syntax

   The correct syntax uses the fully qualified class name with ::class keyword.

3. Final Answer:

   'checkAge' => \App\Http\Middleware\CheckAge::class, -> Option A

4. Quick Check:

   Middleware registration uses class reference [OK]

Hint: Use full class path with ::class to register middleware [OK]

Common Mistakes:

• Using string names instead of class references
• Instantiating middleware instead of referencing class
• Using incorrect keys or formats

3. Given the following Kernel.php snippet, what middleware will be applied when accessing the route /profile?

protected $routeMiddleware = [
    'auth' => \App\Http\Middleware\Authenticate::class,
    'verified' => \App\Http\Middleware\EnsureEmailIsVerified::class,
];

Route::middleware(['auth', 'verified'])->get('/profile', function () {
    return 'User Profile';
});

medium

A. Both 'auth' and 'verified' middleware run

B. Only the 'auth' middleware runs

C. No middleware runs

D. Only the 'verified' middleware runs

Solution

1. Step 1: Check middleware registration

   Both 'auth' and 'verified' middleware are registered in $routeMiddleware.

2. Step 2: Analyze route middleware assignment

   The route applies both middleware by listing them in the array ['auth', 'verified'].

3. Final Answer:

   Both 'auth' and 'verified' middleware run -> Option A

4. Quick Check:

   Route middleware array applies all listed middleware [OK]

Hint: All middleware in array run in order [OK]

Common Mistakes:

• Assuming only one middleware runs
• Confusing middleware registration with application
• Ignoring middleware order

4. Identify the error in this middleware registration snippet inside Kernel.php:

protected $routeMiddleware = [
    'admin' => App\Http\Middleware\AdminCheck,
];

medium

A. Middleware should be registered in $middleware property

B. Middleware name 'admin' is invalid

C. Missing the ::class keyword after the middleware class name

D. Namespace should not be used in Kernel.php

Solution

1. Step 1: Review middleware registration syntax

   Middleware classes must be referenced with the ::class keyword to provide the full class name as a string.

2. Step 2: Identify missing part

   The snippet misses ::class after App\Http\Middleware\AdminCheck.

3. Final Answer:

   Missing the ::class keyword after the middleware class name -> Option C

4. Quick Check:

   Middleware class references need ::class [OK]

Hint: Always add ::class after middleware class name [OK]

Common Mistakes:

• Omitting ::class causing syntax errors
• Registering middleware in wrong property
• Using invalid middleware names

5. You want to create a middleware that logs every request to a specific route group. After creating the middleware class, what is the correct way to register and apply it to the route group in Laravel?

hard

A. Use the middleware class name as a string in the route group without registration

B. Add the middleware class directly inside the route group without registration

C. Register the middleware in $middleware property and apply it only to the route group

D. Register the middleware in Kernel.php under $routeMiddleware with a name, then apply it in the route group using middleware('name')

Solution

1. Step 1: Register middleware properly

   Custom middleware must be registered in $routeMiddleware in Kernel.php with a key name.

2. Step 2: Apply middleware to route group

   Use the registered name in the route group with middleware('name') to apply it.

3. Final Answer:

   Register the middleware in Kernel.php under $routeMiddleware with a name, then apply it in the route group using middleware('name') -> Option D

4. Quick Check:

   Register then apply by name for route groups [OK]

Hint: Register middleware name, then use it in route groups [OK]

Common Mistakes:

• Skipping registration and using class name directly
• Registering middleware globally instead of route-specific
• Misplacing middleware registration property