Doctrine : Fix ManyToOne relationships when the value in database is 0 instead of NULL

CleanAssociationsTrait.php

<?php

use Doctrine\ORM\Mapping as ORM;
use Doctrine\ORM\Event\LifecycleEventArgs;

/**
 * Trait CleanAssociationsTrait
 *
 * This trait is intended to fix the Doctrine ManyToOne relationships when the stored value in database is a 0 instead of NULL.
 * Sometimes you plug Doctrine on an existing database without foreign key support.
 *
 * When you have a Book entry with Id 1 and a id_author with value 1, Doctrine that the book #1 refers to the author #1. $book->getAuthor() should return an Author entity.
 * When you have a Book entry with Id 2 and a NULL id_author, Doctrine knows that the book #1 doesn't have an author (provided you authorized a ManyToOne with nullable = true). $book->getAuthor() should return null.
 * When you have a Book entry with Id 3 and a id_author with value 0, Doctrine throws an "Entity not found" exception.
 *
 * This trait, used in your Book entity, will force the author property to be set to null instead of 0.
 * Then, $book->getAuthor() will return null instead of throwing an "Entity not found" exception.
 * 
 * To use it, add the @ORM\HasLifecycleCallbacks() annotation on top of your entity, and use the trait in it (see example usage below)
 */
trait CleanAssociationsTrait {

    /**
     * @ORM\PostLoad()
     */
    public function cleanAssociations(LifecycleEventArgs $eventArgs) {

        $entity = $eventArgs->getEntity();
        $data   = $eventArgs->getEntityManager()->getUnitOfWork()->getOriginalEntityData($entity);

        # For each association
        foreach ($eventArgs->getEntityManager()->getClassMetadata(get_class($entity))->getAssociationMappings() AS $associationMapping) {

            # Check if it's a ManyToOne relationship
            if (isset($associationMapping['fieldName']) && isset($associationMapping['joinColumns']) && is_array($associationMapping['joinColumns']) && count($associationMapping['joinColumns']) === 1 && isset($associationMapping['joinColumns'][0]['name'])) {

                # Get relation fieldName and the associated column name
                $fieldName  =   $associationMapping['fieldName'];
                $columnName =   $associationMapping['joinColumns'][0]['name'];

                # Check raw data == 0 => set field to null
                if ($data[$columnName] == 0 && is_callable([$entity, 'set' . $fieldName]))
                    $entity->{'set'.$fieldName}(null);
            }
        }
    }

}

# Example usage :
#
#/**
# * @ORM\Table(name="book")
# * @ORM\Entity
# * @ORM\HasLifecycleCallbacks()
# */
#class Book {
# 
#     use CleanAssociationsTrait;
# 
#     /**
#      * @var integer
#      *
#      * @ORM\Column(name="id", type="integer", nullable=false)
#      * @ORM\Id
#      * @ORM\GeneratedValue(strategy="IDENTITY")
#      */
#     protected $idBook;
# 
#     /**
#      * @var Author
#      * @ORM\ManyToOne(targetEntity="Author")
#      * @ORM\JoinColumn(name="id_author", referencedColumnName="id")
#      */
#     protected $author;
# 
#}

Hi thanks for this code. But I found another way to fix it, without any code.

The reason that you will have 0 instead of NULL in your relationship field in you database table is because you added the ManyToOne relationship later in your Entity, at that moment you had already data in you database. From that instance all your current rows will have the relationshipfield set to 0 instead of NULL.

To fix it, replace all 0 entries in you relationship field by hand to NULL. It will never occur again in the future.
Doctrine will set all your future entries without relationship automatically to NULL.

Hi, thanks for such a solution.
Can I extend this and set to null if the relation is not 0 but doesn't exist anymore?
Thanks)

Very useful for migrating an old database to Doctrine ! Thanks

Thanks for this. It helps me in my scenario, although I'm not sure it will work if you are trying to eager load data as it may attempt to load the joined record, and I've not tested what it will do if/when no assocaited record is returned.

@basepack it's not as simple as jus converting the 0 values to nulls, since,i f you still have a legacy system reading the database and expecting the values to be 0, this this is likely to break that legacy system.

In case it's useful, here's my updated version using property types, and attributes…

<?php

declare(strict_types=1);

namespace App\Entity;

use Doctrine\ORM\Event\LifecycleEventArgs;
use Doctrine\ORM\Mapping as ORM;

/**
 * Trait CleanAssociationsTrait
 *
 * This trait is intended to fix the Doctrine ManyToOne relationships when the stored value in database is a 0 instead
 * of NULL.
 * Sometimes you plug Doctrine on an existing database without foreign key support.
 *
 * - When you have a Book entry with Id 1 and a id_author with value 1, Doctrine that the book #1 refers to the author
 *   #1. $book->getAuthor() should return an Author entity.
 * - When you have a Book entry with Id 2 and a NULL id_author, Doctrine knows that the book #1 doesn't have an author
 *   (provided you authorized a ManyToOne with nullable = true). $book->getAuthor() should return null.
 * - When you have a Book entry with Id 3 and a id_author with value 0, Doctrine throws an "Entity not found" exception.
 *
 * This trait, used in your Book entity, will force the author property to be set to null instead of 0.
 * Then, $book->getAuthor() will return null instead of throwing an "Entity not found" exception.
 *
 * To use it, add the #[HasLifecycleCallbacks] annotation on top of your entity, and use the trait in it (see
 * example usage below)
 */
trait CleanAssociationsTrait
{
    #[ORM\PostLoad]
    public function cleanAssociations(LifecycleEventArgs $eventArgs): void
    {
        $entity = $eventArgs->getObject();
        $entityManager = $eventArgs->getObjectManager();
        $data = $entityManager->getUnitOfWork()->getOriginalEntityData($entity);

        $classMetadata = $entityManager->getClassMetadata(get_class($entity));
        # For each association
        foreach ($classMetadata->getAssociationMappings() as $associationMapping) {
            # Check if it's a ManyToOne relationship
            if (
                isset($associationMapping['fieldName'], $associationMapping['joinColumns'][0]['name'])
                && is_array($associationMapping['joinColumns'])
                && count($associationMapping['joinColumns']) === 1
            ) {
                # Get relation fieldName and the associated column name
                $fieldName = $associationMapping['fieldName'];
                $columnName = $associationMapping['joinColumns'][0]['name'];

                # Check raw data == 0 => set field to null
                if (0 === $data[$columnName] && is_callable([$entity, 'set' . $fieldName])) {
                    $entity->{'set' . $fieldName}(null);
                }
            }
        }
    }
}

//  Example usage :
//
// #[ORM\Table(name="book")]
// #[ORM\Entity]
// #[ORM\HasLifecycleCallbacks()]
// class Book {
//
//     use CleanAssociationsTrait;
//
//     #[ORM\Column(name="id", type="integer", nullable=false)]
//     #[ORM\Id]
//     #[ORM\GeneratedValue(strategy="IDENTITY")]
//     protected integer $idBook;
//
//     #[ORM\ManyToOne(targetEntity="Author")]
//     #[ORM\JoinColumn(name="id_author", referencedColumnName="id")]
//     protected Author $author;
// }