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Middlewares and Handlers

Middlewares and handlers are essentials parts of Peak Applications stack. Their job is to simply receive a request, do stuff and call the next middleware or return a response whenever possible. They are also fully compatible with PSR-7 and PSR-15.

Middleware

use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface as Handler;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;

class ClimbMiddleware implements MiddlewareInterface
{
    /**
     * Process an incoming server request and return a response, optionally delegating
     * response creation to a handler.
     */
    public function process(Request $request, Handler $handler): Response 
    {
        // do something ...
        // and finish by calling the next middleware
        return $handler->handle($request);
        // or 
        return new Response('Hello mountains!');
    }
}

Handlers

The main difference with middlewares is that with handlers, you must return a response. You cannot pass the request to the next middleware.

use Psr\Http\Server\RequestHandlerInterface as Handler;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Message\ResponseInterface as Response;

class HandlerA implements Handler
{
    /**
     * Handle the request and return a response.
     */
    public function handle(Request $request): Response
    {
        // ...
        return new Response('Hello mountains!');
    }
}  

Closure middleware

You can also write middlewares and handlers with closure. Underneath, they are wrapped in Peak\Http\Middleware\CallableMiddleware which is PSR-15 compliant.

One of the downside of using closure is that they are less reusable outside your application. Also, it is generally not a good idea to use closure for complex middleware, but for small task and prototyping, they comes really handy.

$myMiddleware = function ($request, $handler) {
    // ... do stuff
    return $handler->handle($request);
}

$myHandler = function ($request) {
    // ... do stuff
    return new Response('...');
}