$mw1 = function ($request, $response, $next) {echo('middleware 1  start <br>');$response = $next($request, $response);echo('middleware 1  end <br>');return $response;
};$mw2 = function ($request, $response, $next) {echo('middleware 2  start <br>');$response = $next($request, $response);echo('middleware 2  end <br>');return $response;
};$app->get('/mw', function ($request, $response, $args) {echo(' Hello <br>');return $response;
})->add($mw1)->add($mw2);

protected function addMiddleware(callable $callable)
{if ($this->middlewareLock) {throw new RuntimeException('Middleware can’t be added once the stack is dequeuing');}if (is_null($this->stack)) {$this->seedMiddlewareStack();}$next = $this->stack->top();$this->stack[] = function (ServerRequestInterface $req, ResponseInterface $res) use ($callable, $next) {$result = call_user_func($callable, $req, $res, $next);if ($result instanceof ResponseInterface === false) {throw new UnexpectedValueException('Middleware must return instance of \Psr\Http\Message\ResponseInterface');}return $result;};return $this;
}

        if ($this->outputBuffering === false) {$newResponse = $handler($this->callable, $request, $response, $this->arguments);} else {try {ob_start();$newResponse = $handler($this->callable, $request, $response, $this->arguments);$output = ob_get_clean();} catch (Exception $e) {ob_end_clean();throw $e;}}

        if (!empty($output) && $response->getBody()->isWritable()) {if ($this->outputBuffering === 'prepend') {// prepend output buffer content$body = new Http\Body(fopen('php://temp', 'r+'));$body->write($output . $response->getBody());$response = $response->withBody($body);} elseif ($this->outputBuffering === 'append') {// append output buffer content$response->getBody()->write($output);}}