Doctrine\ORM\EntityManager::lock PHP Method

    public function lock($entity, $lockMode, $lockVersion = null)
    {
        $this->unitOfWork->lock($entity, $lockMode, $lockVersion);
    }

 /**
  * Finds an entity by its primary key / identifier.
  *
  * @param $id The identifier.
  * @param int $lockMode
  * @param int $lockVersion
  * @return object The entity.
  */
 public function find($id, $lockMode = LockMode::NONE, $lockVersion = null)
 {
     // Check identity map first
     if ($entity = $this->_em->getUnitOfWork()->tryGetById($id, $this->_class->rootEntityName)) {
         if ($lockMode != LockMode::NONE) {
             $this->_em->lock($entity, $lockMode, $lockVersion);
         }
         return $entity;
         // Hit!
     }
     if (!is_array($id) || count($id) <= 1) {
         // @todo FIXME: Not correct. Relies on specific order.
         $value = is_array($id) ? array_values($id) : array($id);
         $id = array_combine($this->_class->identifier, $value);
     }
     if ($lockMode == LockMode::NONE) {
         return $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id);
     } else {
         if ($lockMode == LockMode::OPTIMISTIC) {
             if (!$this->_class->isVersioned) {
                 throw OptimisticLockException::notVersioned($this->_entityName);
             }
             $entity = $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id);
             $this->_em->getUnitOfWork()->lock($entity, $lockMode, $lockVersion);
             return $entity;
         } else {
             if (!$this->_em->getConnection()->isTransactionActive()) {
                 throw TransactionRequiredException::transactionRequired();
             }
             return $this->_em->getUnitOfWork()->getEntityPersister($this->_entityName)->load($id, null, null, array(), $lockMode);
         }
     }
 }