vendor/symfony/http-kernel/EventListener/DisallowRobotsIndexingListener.php line 27
<?php/** This file is part of the Symfony package.** (c) Fabien Potencier <fabien@symfony.com>** For the full copyright and license information, please view the LICENSE* file that was distributed with this source code.*/namespace Symfony\Component\HttpKernel\EventListener;use Symfony\Component\EventDispatcher\EventSubscriberInterface;use Symfony\Component\HttpKernel\Event\ResponseEvent;use Symfony\Component\HttpKernel\KernelEvents;/*** Ensures that the application is not indexed by search engines.** @author Gary PEGEOT <garypegeot@gmail.com>*/class DisallowRobotsIndexingListener implements EventSubscriberInterface{private const HEADER_NAME = 'X-Robots-Tag';public function onResponse(ResponseEvent $event): void{if (!$event->getResponse()->headers->has(static::HEADER_NAME)) {$event->getResponse()->headers->set(static::HEADER_NAME, 'noindex');}}public static function getSubscribedEvents(): array{return [KernelEvents::RESPONSE => ['onResponse', -255],];}}