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    <h3>Editing: MessengerTransportListener.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mailer\EventListener;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Mailer\Event\MessageEvent;
use Symfony\Component\Messenger\Stamp\TransportNamesStamp;
use Symfony\Component\Mime\Message;

/**
 * Allows messages to be sent to specific Messenger transports via the &quot;X-Bus-Transport&quot; MIME header.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
final class MessengerTransportListener implements EventSubscriberInterface
{
    public function onMessage(MessageEvent $event): void
    {
        if (!$event-&gt;isQueued()) {
            return;
        }

        $message = $event-&gt;getMessage();
        if (!$message instanceof Message || !$message-&gt;getHeaders()-&gt;has('X-Bus-Transport')) {
            return;
        }

        $names = $message-&gt;getHeaders()-&gt;get('X-Bus-Transport')-&gt;getBody();
        $names = array_map('trim', explode(',', $names));
        $event-&gt;addStamp(new TransportNamesStamp($names));
        $message-&gt;getHeaders()-&gt;remove('X-Bus-Transport');
    }

    public static function getSubscribedEvents(): array
    {
        return [
            MessageEvent::class =&gt; 'onMessage',
        ];
    }
}
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