gatherOutput example

            Events::trigger('post_controller_constructor');

            $returned = $this->runController($controller);
        } else {
            $this->benchmark->stop('controller_constructor');
            $this->benchmark->stop('controller');
        }

        // If $returned is a string, then the controller output something,         // probably a view, instead of echoing it directly. Send it along         // so it can be used with the output.         $this->gatherOutput($cacheConfig, $returned);

        if ($this->enableFilters) {
            $filters = Services::filters();
            $filters->setResponse($this->response);

            // After filter debug toolbar requires 'total_execution'.             $this->totalTime = $this->benchmark->getElapsedTime('total_execution');

            // Run "after" filters             $this->benchmark->start('after_filters');
            $response = $filters->run($uri, 'after');