Middleware is one of the important part of any application. The code which we want to stick between request/response life cycle which is not necessary part of our application logic. That is called as middleware.

Let take a example to know more about middleware.

1)   Adding session support
2)   Parsing query strings
3)   Implementing rate-limiting
4)   Sniffing for bot traffic
5)   Adding logging
6)   Parsing request JSON
7)  Anything else related to the request/response lifecycle

Laravel's Implementation Step By Step:

For implement middleware we use HttpKernelInterface. In laravel 4.x we have Foundation/Application (In built functionality). By adding this we are able to integrate middle ware in laravel.

Example:

Middleware may be specified on controller routes like so:

Route::get('profile', [
    'middleware' => 'auth',
    'uses' => 'UserController@showProfile'
]);

Additionally, you may specify middleware within your controller's constructor:

class UserController extends Controller {

    /**
     * Instantiate a new UserController instance.
     */
    public function __construct()
    {
        $this->middleware('auth');

        $this->middleware('log', ['only' => ['fooAction', 'barAction']]);

        $this->middleware('subscribed', ['except' => ['fooAction', 'barAction']]);
    }

}