Symfony ORM inheritance

I have my 3 Entities :

Book, Cd, Dvd

They all 3 shares some properties :

id, title, reference_number...

I want to regroup them into a Parent Class named Document here’s my actual code :

class Cd extends Document
{
    /**
     * @ORMColumn(type="integer")
     */
    private $total_duration;
}


class Dvd extends Document
{

   /**
     * @ORMColumn(type="boolean")
    */
    private $has_bonus;
}

class Novel extends Document
{

   /**
     * @ORMColumn(type="integer")
    */
    private $pages;
}

and my Document class :

abstract class Document
{
    /**
     * @ORMId
     * @ORMGeneratedValue
     * @ORMColumn(type="integer")
     */
    private $id;

   /**
    * @ORMColumn(type="string", length=255)
    */
   private $title;


   /**
    * @ORMColumn(type="string", length=255)
    */
   private $reference_number;
}

To retrieve the ID of my entities I use the Document method :

   protected function getId(): ?int
{
    return $this->id;
}

However I had to implement into my child classes the method :

   public function getId(): ?int
{
    return parent::getId();
}

for some Twig/EasyAdmin reasons.

Is it a good practice or is there another way to build this inheritance? I’m currently dealing with some troubles with the Edit part from EasyAdmin 3 telling me that the Id cannot be retrieved (the reason of the question).
I’m genuinely looking for some docs or whatever that could explain the good pratices. Thanks

Source: Symfony Questions