Doctrine\ORM\UnitOfWork::doPersist PHP Method

    private function doPersist($entity, array &$visited)
    {
        $oid = spl_object_hash($entity);
        if (isset($visited[$oid])) {
            return; // Prevent infinite recursion
        }

        $visited[$oid] = $entity; // Mark visited

        $class = $this->em->getClassMetadata(get_class($entity));

        // We assume NEW, so DETACHED entities result in an exception on flush (constraint violation).
        // If we would detect DETACHED here we would throw an exception anyway with the same
        // consequences (not recoverable/programming error), so just assuming NEW here
        // lets us avoid some database lookups for entities with natural identifiers.
        $entityState = $this->getEntityState($entity, self::STATE_NEW);

        switch ($entityState) {
            case self::STATE_MANAGED:
                // Nothing to do, except if policy is "deferred explicit"
                if ($class->isChangeTrackingDeferredExplicit()) {
                    $this->scheduleForDirtyCheck($entity);
                }
                break;
            case self::STATE_NEW:
                $this->persistNew($class, $entity);
                break;
            case self::STATE_REMOVED:
                // Entity becomes managed again
                unset($this->entityDeletions[$oid]);
                $this->entityStates[$oid] = self::STATE_MANAGED;
                break;
            case self::STATE_DETACHED:
                // Can actually not happen right now since we assume STATE_NEW.
                throw new InvalidArgumentException("Detached entity passed to persist().");
            default:
                throw new UnexpectedValueException("Unexpected entity state: $entityState.");
        }

        $this->cascadePersist($entity, $visited);
    }