The Scotch.io site has posted a tutorial that aims to help you understand middleware in Laravel applications - how they work and how to create ones based on your custom needs.

HTTP Middlewares provide a convenient mechanism for filtering HTTP requests entering your application. Laravel, for example, has a middleware for verifying a user's authentication.

These are some cases where I have had to resort to using middleware. There are many more cases where you would like to use a middleware. [...] By the end of this article, you should be able to create a middleware, registers it and use it in your projects. We will be illustrating the creation till usage of middlewares by creating one of our own. Our middleware will enable maintenance either site-wide or on some routes.

They start by creating a middleware (theirs is DownForMaintenance) and how to register it with Laravel as a valid middleware option. By default they will execute with every request but you can narrow them down to only happening on certain routes (examples included). There's also mentions of middleware parameters, grouping middleware and deferring the response return until after other code is executed.