Problem Symfony/Doctrine : One-To-Many - Self-referencing on a primary key - symfony

Question

I would like to have a "post" with an identifier. This one could be classified in another "post" by storing the identifier of his parent.
I tried to do like this:
class Post {
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
* #ORM\OneToMany(targetEntity="Post", mappedBy="Id_Post_Parent")
*/
private $Id_Post;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\Post", inversedBy="Id_Post")
* #ORM\JoinColumn(name="Id_Post", referencedColumnName="Id_Post", nullable=true)
*/
private $Id_Post_Parent;
...
}
but I have this error when i'm checking with doctrine:schema:validate :
[FAIL] The entity-class App\Entity\Post mapping is invalid:
The association App\Entity\Post#Id_Post_Parent refers to the inverse side field App\Entity\Post#Id_Post which is not defined as association.
The association App\Entity\Post#Id_Post_Parent refers to the inverse side field App\Entity\Post#Id_Post which does not exist.
The referenced column name 'Id_Post' has to be a primary key column on the target entity class 'App\Entity\Post'.
Can someone help me to fix this ?

Answer 1

There is small logical error with your structure - your ID_Post variable tries to be both the primary key (the ID) and the collection association side. I didn't check this syntax in too much details (you can find an example of this association along with most of the other associations from doctrine documentation: https://www.doctrine-project.org/projects/doctrine-orm/en/2.6/reference/association-mapping.html#one-to-many-self-referencing), but basically you need to add the children association separately to your entity like this:
class Post
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\ManyToOne(targetEntity="Post", inversedBy="postChildren")
* #ORM\JoinColumn(name="id_parent_post", referencedColumnName="id", nullable=true)
*/
private $postParent;
/**
* #ORM\OneToMany(targetEntity="Post", mappedBy="postParent")
*/
private $postChildren;
public function __construct() {
$this->postChildren = new \Doctrine\Common\Collections\ArrayCollection();
}
}