Doctrine\ODM\PHPCR\UnitOfWork::doMergeSingleDocumentProperty PHP Method

    private function doMergeSingleDocumentProperty($managedCopy, $document, \ReflectionProperty $prop, array $mapping)
    {
        if (null === $document) {
            $prop->setValue($managedCopy, null);
        } elseif (!($mapping['cascade'] & ClassMetadata::CASCADE_MERGE)) {
            if ($this->getDocumentState($document) == self::STATE_MANAGED) {
                $prop->setValue($managedCopy, $document);
            } else {
                $targetClass = $this->dm->getClassMetadata(get_class($document));
                $id = $this->determineDocumentId($document, $targetClass);
                $proxy = $this->getOrCreateProxy($id, $targetClass->name);
                $prop->setValue($managedCopy, $proxy);
                $this->registerDocument($proxy, $id);
            }
        }
    }