<?php tag missing in code during 13 "Managing the Lifecycle of Doctrine Objects"

[TrackLab]

During the Chapter "Managing the Lifecycle of Doctrine Objects", one is asked to create a Doctrine entity listener. With a block of code to copy.

The code block forgets to add a <?php tag in the beginning, resulting in the document being displayed as HTML Text over the website.
Without knowing about the needed tag, this is a weird behaviour without obvious solution.

The fixed code would be

<?php

namespace App\EntityListener;

use App\Entity\Conference;
use Doctrine\Persistence\Event\LifecycleEventArgs;
use Symfony\Component\String\Slugger\SluggerInterface;

class ConferenceEntityListener
{
    public function __construct(
        private SluggerInterface $slugger,
    ) {
    }

    public function prePersist(Conference $conference, LifecycleEventArgs $event)
    {
        $conference->computeSlug($this->slugger);
    }

    public function preUpdate(Conference $conference, LifecycleEventArgs $event)
    {
        $conference->computeSlug($this->slugger);
    }
}