# How to create a middleware in Laravel?

Creating middleware in Laravel is a common task that helps to filter HTTP requests entering your application. Middleware can perform various tasks such as authentication, logging, and modifying request/response objects.

### Step 1: Create Middleware

You can create middleware using the Artisan command-line tool. Open your terminal and run the following command:

```php
php artisan make:middleware CheckAge
```

This will create a new middleware class named `CheckAge` in the `app/Http/Middleware` directory.

### Step 2: Define Middleware Logic

Open the newly created middleware file (`app/Http/Middleware/CheckAge.php`) and define the logic you want to apply. For example, you might want to check if the user is above a certain age:

```php
namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class CheckAge
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle(Request $request, Closure $next)
    {
        if ($request->age <= 18) {
            return redirect('home');
        }

        return $next($request);
    }
}
```

In this example, the middleware checks if the `age` parameter in the request is less than or equal to 18. If so, it redirects the user to the `home` route. Otherwise, it allows the request to proceed further.

### Step 3: Register Middleware

You need to register your middleware in the `app/Http/Kernel.php` file. Middleware can be registered globally, assigned to specific routes, or grouped.

#### Registering Globally

To apply middleware to every request globally, add it to the `$middleware` array in the `app/Http/Kernel.php` file:

```php
protected $middleware = [
    // ...
    \App\Http\Middleware\CheckAge::class,
];
```

#### Registering as Route Middleware

If you want to use the middleware on specific routes, add it to the `$routeMiddleware` array:

```php
protected $routeMiddleware = [
    // ...
    'check.age' => \App\Http/Middleware\CheckAge::class,
];
```

### Step 4: Use Middleware in Routes

Once the middleware is registered, you can use it in your routes or controllers. Open the `routes/web.php` file and apply the middleware to specific routes:

```php
Route::get('profile', function () {
    // Only users older than 18 can access this route
})->middleware('check.age');
```

Or apply it to a group of routes:

```php
Route::group(['middleware' => ['check.age']], function () {
    Route::get('profile', function () {
        // Only users older than 18 can access this route
    });

    Route::get('settings', function () {
        // Only users older than 18 can access this route
    });
});
```

### Step 5: Testing Middleware

You should test your middleware to ensure it works as expected. Create test cases or manually test different scenarios to verify the middleware's behavior.

### Example Test Scenario

To manually test, you can use a URL with different `age` query parameters to see if the redirection works:

```php
httpCopy codehttp://your-app.test/profile?age=17  // This should redirect to 'home'
http://your-app.test/profile?age=19  // This should allow access to 'profile'
```