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

    private function computeAssociationChanges($document, $class, $oid, $isNew, $changeSet, $assocType)
    {
        switch ($assocType) {
            case 'reference':
                $mappings = $class->referenceMappings;
                $computeMethod = 'computeReferenceChanges';
                break;
            case 'referrer':
                $mappings = $class->referrersMappings;
                $computeMethod = 'computeReferrerChanges';
                break;
            default:
                throw new InvalidArgumentException('Unsupported association type used: ' . $assocType);
        }
        foreach ($mappings as $fieldName) {
            $mapping = $class->mappings[$fieldName];
            if (ClassMetadata::MANY_TO_MANY === $mapping['type'] && 'reference' === $assocType || 'referrers' === $mapping['type'] && 'referrer' === $assocType) {
                if ($changeSet[$fieldName] instanceof PersistentCollection) {
                    if (!$changeSet[$fieldName]->isInitialized()) {
                        continue;
                    }
                } else {
                    if (null === $changeSet[$fieldName]) {
                        $changeSet[$fieldName] = array();
                    }
                    if (!is_array($changeSet[$fieldName]) && !$changeSet[$fieldName] instanceof Collection) {
                        throw PHPCRException::associationFieldNoArray(self::objToStr($document, $this->dm), $fieldName);
                    }
                    // convert to a PersistentCollection
                    switch ($assocType) {
                        case 'reference':
                            $targetDocument = isset($mapping['targetDocument']) ? $mapping['targetDocument'] : null;
                            $changeSet[$fieldName] = ReferenceManyCollection::createFromCollection($this->dm, $document, $mapping['property'], $changeSet[$fieldName], $targetDocument, !$isNew);
                            break;
                        case 'referrer':
                            $referringMeta = $this->dm->getClassMetadata($mapping['referringDocument']);
                            $referringField = $referringMeta->mappings[$mapping['referencedBy']];
                            $changeSet[$fieldName] = ReferrersCollection::createFromCollection($this->dm, $document, $changeSet[$fieldName], $referringField['strategy'], $referringField['property'], $mapping['referringDocument'], !$isNew);
                            break;
                    }
                    $class->setFieldValue($document, $fieldName, $changeSet[$fieldName]);
                    $this->originalData[$oid][$fieldName] = $changeSet[$fieldName];
                }
                $coid = spl_object_hash($changeSet[$fieldName]);
                $this->visitedCollections[$coid] = $changeSet[$fieldName];
                foreach ($changeSet[$fieldName] as $association) {
                    if ($association !== null) {
                        $this->{$computeMethod}($mapping, $association);
                    }
                }
                if (!$isNew && $mapping['cascade'] & ClassMetadata::CASCADE_REMOVE) {
                    if (!$this->originalData[$oid][$fieldName] instanceof PersistentCollection) {
                        throw new RuntimeException("OriginalData for a collection association contains something else than a PersistentCollection.");
                    }
                    $associations = $this->originalData[$oid][$fieldName]->getOriginalPaths();
                    foreach ($associations as $association) {
                        $association = $this->getDocumentById($association);
                        if ($association && !$this->originalData[$oid][$fieldName]->contains($association)) {
                            $this->scheduleRemove($association);
                        }
                    }
                }
            } elseif ($changeSet[$fieldName] && ClassMetadata::MANY_TO_ONE === $mapping['type'] && 'reference' === $assocType) {
                $this->computeReferenceChanges($mapping, $changeSet[$fieldName]);
            }
        }
    }