# Uncaught Error: Cannot instantiate interface

**URL:** <https://discourse.slimframework.com/t/uncaught-error-cannot-instantiate-interface/4157>\
**Category:** Questions\
**Created:** [May 12, 2020, 11:47pm UTC](https://discourse.slimframework.com/t/uncaught-error-cannot-instantiate-interface/4157 "2020-05-12T23:47:20Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![kingrenz23](https://avatars.discourse-cdn.com/v4/letter/k/c2a13f/32.png) [@kingrenz23](https://discourse.slimframework.com/u/kingrenz23)\
**Post date:** [May 12, 2020, 11:47pm UTC](https://discourse.slimframework.com/t/uncaught-error-cannot-instantiate-interface/4157/1 "2020-05-12T23:47:20Z")

</div>

I’m adding a middle-ware to check or verify if the request data from the client is a valid json  
then return an error message.

But got stock with this error. Please help me here

```auto
    <br />
    <b>Fatal error</b>: Uncaught Error: Cannot instantiate interface 
    Psr\Http\Message\ResponseInterface in
    C:\xampp\htdocs\learning_app\public\index.php:51
    Stack trace:
    #0 C:\xampp\htdocs\learning_app\public\index.php(59): Renz- 
    &gt;handle(Object(Slim\Psr7\Request))
    #1 C:\xampp\htdocs\learning_app\vendor\slim\slim\Slim\MiddlewareDispatcher.php(283):
    {closure}(Object(Slim\Psr7\Request), Object(Renz))
    #2 C:\xampp\htdocs\learning_app\vendor\slim\slim\Slim\MiddlewareDispatcher.php(81):
    class@anonymous-&gt;handle(Object(Slim\Psr7\Request))
    #3 C:\xampp\htdocs\learning_app\vendor\slim\slim\Slim\App.php(211):
    Slim\MiddlewareDispatcher-&gt;handle(Object(Slim\Psr7\Request))
    #4 C:\xampp\htdocs\learning_app\vendor\slim\slim\Slim\App.php(195): Slim\App- 
    &gt;handle(Object(Slim\Psr7\Request))
    #5 C:\xampp\htdocs\learning_app\public\index.php(130): Slim\App-&gt;run()
    #6 {main}
    thrown in <b>C:\xampp\htdocs\learning_app\public\index.php</b> on line <b>51</b><br />

```

here is my code

```php
        <?php
          use Psr\Http\Message\ResponseInterface as Response;
          use Psr\Http\Message\ServerRequestInterface as Request;
          use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
          use Slim\Factory\AppFactory;
          use ReallySimpleJWT\Token;
          use ReallySimpleJWT\Parse;
          use ReallySimpleJWT\Jwt;
          use ReallySimpleJWT\Validate;
          use ReallySimpleJWT\Encode;
          use ReallySimpleJWT\Exception\ValidateException;

          require __DIR__. '/../vendor/autoload.php';
          require __DIR__. '/../config/connection.php';

         $app = AppFactory::create();
         $app->setBasePath('/learning_app');

         class Renz implements RequestHandler{
	            public function handle(Request $request): Response{
		
		            $data = $request->getBody();
	   
		try{
			$json = json_decode($data);
			
			$status = 200;
			$headers = [
				"Content-Type" => "application/json"
			];
			
			$body = array(
				"ok" => true,
				"message" => "mayat"
			);
			
		}catch(Exception $e){
			
			$status = 500;
			$headers = [
				"Content-Type" => "application/json"
			];
			
			$body = array(
				"ok" => false,
				"message" => "invalid request"
			);
			
		}
		
		$response = new Response($status, $headers, $body); //this is line 51 in the error
		
		return $response;
	}
    }

    $beforeMiddleware = function (Request $request, RequestHandler $handler) {
	  $handler = new Renz();
	  $response = $handler->handle($request);
    
          return $response;
    };

    $app->add($beforeMiddleware);

    .....

    $app->run();

```

---

<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:** [May 13, 2020, 5:13pm UTC](https://discourse.slimframework.com/t/uncaught-error-cannot-instantiate-interface/4157/2 "2020-05-13T17:13:59Z")

</div>

Try to use the ResponseFactory (Slim 4) or declare the real class and not the interface.

> [@kingrenz23](#):
>
> `use Psr\Http\Message\ResponseInterface as Response;`