What this warning means?
MyPackage\Handlers\ErrorHandler::__invoke(Slim\Http\Request $request, Slim\Http\Response $response, Exception $exception)
should be compatible with
Slim\Handlers\Error::__invoke(Psr\Http\Message\ServerRequestInterface $request, Psr\Http\Message\ResponseInterface $response, Exception $exception)
I receive this warning only on a server with PHP 7.0, it’s ok on 5.6.