PSR-15 – HTTP Server Request Handlers (middleware)

The middleware interface in PSR-15 has the following abstraction:

// Psr\Http\Server\MiddlewareInterface

namespace Psr\Http\Server;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\RequestHandlerInterface;

interface MiddlewareInterface
{
    public function process(
        ServerRequestInterface $request,
        RequestHandlerInterface $handler
    ) : ResponseInterface;
}

Again, you can see it is a very simple interface. It only has one specified public method process for middleware implementation. The component (middleware) that implements this interface will only accept a PSR-7 HTTP request message and a PSR-15 HTTP server request handler and then must return a PSR-7 HTTP response message.

We will use the zend-stratigility components from Zend Framework, which implement this interface, to allow us to create PSR-15 middleware in our app. Let's learn how to get it hooked...