How to write

Slim application middleware must subclass \Slim\Middleware and implement a public call() method. The call() method does not accept arguments. Middleware may implement its own constructor, properties, and methods. I encourage you to look at Slim’s built-in middleware for working examples (e.g. Slim/Middleware/ContentTypes.php or Slim/Middleware/SessionCookie.php).

This example is the simplest implementation of Slim application middleware. It extends \Slim\Middleware, implements a public call() method, and calls the next inner middleware.

<?php
class MyMiddleware extends \Slim\Middleware
{
    public function call()
    {
        $this->next->call();
    }
}