Time by time you have to extend a entity. Doctrine is a powerful ORM and of course this case is covered at all. Doctrine comes with several type of inheritance. The Mapped Superclass, Single- and Multiple table inheritance.

But they have all something in common. You have declare inheritance in the mapping file of entity you want to extend from. This is no problem if you can edit this file. But what if this file live in the vendor directory because it is package?

Then you can only hook into doctrine with a listener and change the mapping information of the entity. This is indeed uncomfortable. So this extension will help you to make it a bit more easy by only adding some meta information to the config.

Because the most use case is to extend a given entity to add a few properties you need, the only supported inheritance type is the single table inheritance. So let’s have a deeper look how it works.

Single table inheritance

Imagine we have a simple class Person with one property id and name

class Person
    private $id;
    private $name;

    // ... Getter and setters

Then the resulting table is very easy and straight forward.

| id | name          |
| 1  |  Bob          |

But now we will extend our Person entity and add some more information e.g. gender

class GenderPerson extends Person
    private $gender;

    // ... Getter and setters

Because we are using single table inheritance the result will be of course one table, which will be extended by the properties of our GenderPerson and a further discriminator column, so we know what kind of class we are talking about.

| id | name          | gender        | discr    |
| 1  | Bob           | male          | root     |
| 2  | Alice         | female        | app      |


To get the single table inheritance, we only need to tell EnhavoDoctrineExtensionBundle that our class GenderPerson is extending Person and what is the value of the discr column. The entity which you will extend from will automatically have the value root.

Just add following to your config.

            extends: App\Entity\Person
            discrName: 'app'

Multiple hierarchy

Multiple inheritance are also possible. Just add another config and change the discrName so it is unique over your hierarchy.