# Middleware type, and return type

**URL:** <https://discourse.slimframework.com/t/middleware-type-and-return-type/5303>\
**Category:** Questions\
**Created:** [July 1, 2022, 12:41am UTC](https://discourse.slimframework.com/t/middleware-type-and-return-type/5303 "2022-07-01T00:41:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![batuhankucuk](https://avatars.discourse-cdn.com/v4/letter/b/278dde/32.png) [@batuhankucuk](https://discourse.slimframework.com/u/batuhankucuk)\
**Post date:** [July 1, 2022, 12:41am UTC](https://discourse.slimframework.com/t/middleware-type-and-return-type/5303/1 "2022-07-01T00:41:38Z")

</div>

Hello All, I would like to ask 2 questions about use of middlewares in slim. My questions will be about these usages;

**slimphp/Slim-Skeleton usage:**

> <https://github.com/slimphp/Slim-Skeleton/blob/master/src/Application/Middleware/SessionMiddleware.php>

**Official docs usage:**  
[https://www.slimframework.com/docs/v4/concepts/middleware.html#invokable-class-middleware-example](https://www.slimframework.com/docs/v4/concepts/middleware.html#invokable-class-middleware-example)

```auto
<?php
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
use Slim\Psr7\Response;

class ExampleBeforeMiddleware
{
    /**
     * Example middleware invokable class
     *
     * @param ServerRequest $request PSR-7 request
     * @param RequestHandler $handler PSR-15 request handler
     *
     * @return Response
     */
    public function __invoke(Request $request, RequestHandler $handler): Response
    {
        $response = $handler->handle($request);
        $existingContent = (string) $response->getBody();
    
        $response = new Response();
        $response->getBody()->write('BEFORE' . $existingContent);
    
        return $response;
    }
}

```

**Way to impelement**  
Both are official, but from different up to date sources. However, skeleton-one implements Middeware interface thus process() method is implemented, example usage in the docs is also a class middleware yet do not implements any interface and called via \_\_invoke() method. I would like to learn what are the exact difference between this two usages.

**Returning Response**  
The other question is how they return response; usage in the skeleton returns the response handled by the handler, the other is create a new Response object inline and return the new response. I know in some cases it is needed to create new Response from existing one, but again what are the difference and advantage/disadvantage of it.

I looked them up online but could find any useful answers.

Thank you in advance.

P.S.: Currently **slim/slim** package’s **4.10** version is installed, and the project based on **slim/slim-skeleton** composer package.

---

<div class="post-metadata">

**Author:** ![odan](https://avatars.discourse-cdn.com/v4/letter/o/9de053/32.png) [@odan](https://discourse.slimframework.com/u/odan)\
**Post date:** [July 1, 2022, 7:23am UTC](https://discourse.slimframework.com/t/middleware-type-and-return-type/5303/2 "2022-07-01T07:23:13Z")

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Both types of middleware are supported by Slim, the PSR-15 `MiddlewareInterface` with the `process` method and the invokable class with the `__invoke` method. The difference from a usage perspective is that the invokable class is not a real “standard”, like the PSR-15 interfaces. If you plan to use your middlewares in other projects or packages, then better use the PSR-15 `MiddlewareInterface` for all your middlewares. It is also generally recommend to use the MiddlewareInterface.

Returning Response: There is no advantage or disadvantage, because it depends on the use case. One aspect is whether it’ s an inbound or outbound middleware, or even both.