What is Middleware?

In Laravel, Middleware is a filtering mechanism that facilitates filtering of incoming HTTP request before it is routed to particular controller for further processing. Laravel framework includes several in-built middleware, including authentication and CSRF protection. All of these middleware are located in the app/Http/Middleware directory. In addition to the built-in middleware, custom middleware can also be created.

Creating Middleware

Middleware can be created by executing the following artisan command –

Syntex:-

Replace <middleware-name> with name you like for middleware you creating.

For example, we create a middleware that that only allow to admin user to access into admin panel.

Step 1 – So first we create IsAdminMiddleware middleware using following command –

Step 2 – After successful execution of the above command, IsAdminMiddleware.php will be created at app/Http/Middleware. The newly created IsAdminMiddleware.php will have the following code in it –

Step 3 – Ok, now open IsAdminMiddleware.php file and put bellow code on that file.

Registering Middleware

Once our middleware is created, we have to register it before we use it. The middleware is registered at app/Http/Kernel.php. There are two ways we can register a middleware in Kernel.php.

Global Middleware

If you want your middleware to be run on every HTTP request handled by your application, you need to list your middleware class at the end of $middleware array of your app/Http/Kernel.php class.

Route Middleware

If you want your middleware to be run on some specific routes, you need to list your middleware in the $routeMiddleware array of your app/Http/Kernel.php class.

Example:-
We have created IsAdminMiddleware in the above example. Now we can register it in route specific middleware property and create alias for it in Kernel.php file.

Our app/Http/Kernel.php file looks as following –

Once middleware has been created and registered, you can assign it to any route using middleware key in following ways –

Middleware Parameters

Sometime you may want to pass parameters to a Middleware, this can be achieved by passing our custom argument after the $next argument.
The standard middleware funcation looks like as following-

Imagine, if our application has different type of user roles like author, editor, publisher and admin, and now you want to authenticate the request based on user role, this can be achieved by passing user role as parameter to middleware.

In this case our middleware function will look like as following –

We can specify middleware parameters when defining the route by separating the middleware name and parameters with a : and multiple parameters should be delimited by commas(,).

Add the following line of code in app/Http/routes.php file.

Before & After Middleware

Whether a middleware runs before or after a request depends on the middleware itself.

For example, let’s define a middleware that runs before a request –

Now, let’s define a middleware that perform its task after the request –

Terminable Middleware

Terminable middleware allows you to perform some task even after the HTTP response is already been sent to the browser.This can be done by defining a middleware as “terminable” middleware. A middleware can be defined as “terminable” by adding a terminate method to it.The terminate method accepts two arguments $request and $response. Once a terminable middleware is created it should be registered as global middleware in app/Http/Kernel.php file.

Example:-