Registering middleware in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is middleware in Laravel?

Middleware is a way to filter HTTP requests entering your application. It acts like a gatekeeper that can inspect, modify, or reject requests before they reach your routes or controllers.

beginner

How do you register a global middleware in Laravel?

You add the middleware class to the $middleware array inside the app/Http/Kernel.php file. This makes it run on every HTTP request automatically.

beginner

Where do you register route middleware in Laravel?

Route middleware are registered in the $routeMiddleware array inside app/Http/Kernel.php. You give each middleware a key name to use in routes or controllers.

beginner

How do you apply middleware to a specific route in Laravel?

You use the middleware method on the route definition, like Route::get('/profile', 'ProfileController@index')->middleware('auth'); This runs the 'auth' middleware only for that route.

beginner

What is the difference between global and route middleware in Laravel?

Global middleware runs on every HTTP request automatically. Route middleware runs only on routes or groups where you explicitly apply them.

Where do you register global middleware in Laravel?

A In the $routeMiddleware array inside app/Http/Kernel.php

B In the config/app.php file

C In the routes/web.php file

D In the $middleware array inside app/Http/Kernel.php

Global middleware are registered in the $middleware array inside app/Http/Kernel.php to run on every request.

How do you assign a middleware to a specific route?

A Write it inside the controller constructor

B Use the middleware() method on the route definition

C Add it to the $routeMiddleware array only

D Add it to the $middleware array

You assign middleware to a route by calling middleware('name') on the route definition.

What is the purpose of the $routeMiddleware array?

A To list all middleware classes in the project

B To register middleware that runs on every request

C To register middleware that can be applied to specific routes by name

D To configure middleware priority

The $routeMiddleware array maps short names to middleware classes for use on specific routes.

If you want middleware to run on every HTTP request, where should you register it?

A In the $middleware array

B In the $routeMiddleware array

C In the routes file

D In the controller

Middleware in the $middleware array runs globally on every HTTP request.

Which file is the main place to register middleware in Laravel?

A app/Http/Kernel.php

B routes/web.php

C config/middleware.php

D app/Providers/AppServiceProvider.php

Middleware registration happens mainly in app/Http/Kernel.php.

Explain how to register and apply middleware to a route in Laravel.

Think about the $routeMiddleware array and route methods.

Describe the difference between global and route middleware in Laravel.

Consider where each type is registered and when it runs.

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