yii\db\ActiveRecord::isTransactional PHP Method

    public function isTransactional($operation)
    {
        $scenario = $this->getScenario();
        $transactions = $this->transactions();
        return isset($transactions[$scenario]) && $transactions[$scenario] & $operation;
    }

 /**
  * For each related model, try to save it first.
  * If set in the owner model, operation is done in a transactional way so if one of the models should not validate
  * or be saved, a rollback will occur.
  * This is done during the before validation process to be able to set the related foreign keys.
  * @param ActiveRecord $model
  * @param ModelEvent $event
  * @return bool
  */
 public function _saveRelatedRecords(ActiveRecord $model, ModelEvent $event)
 {
     if ($model->isNewRecord && $model->isTransactional($model::OP_INSERT) || !$model->isNewRecord && $model->isTransactional($model::OP_UPDATE) || $model->isTransactional($model::OP_ALL)) {
         $this->_transaction = $model->getDb()->beginTransaction();
     }
     try {
         foreach ($this->relations as $relationName) {
             if (array_key_exists($relationName, $this->_oldRelationValue)) {
                 // Relation was not set, do nothing...
                 $relation = $model->getRelation($relationName);
                 if (!empty($model->{$relationName})) {
                     if ($relation->multiple === false) {
                         // Save Has one relation new record
                         $pettyRelationName = Inflector::camel2words($relationName, true);
                         $this->_saveModelRecord($model->{$relationName}, $event, $pettyRelationName, $relationName);
                     } else {
                         // Save Has many relations new records
                         /** @var ActiveRecord $relationModel */
                         foreach ($model->{$relationName} as $i => $relationModel) {
                             $pettyRelationName = Inflector::camel2words($relationName, true) . " #{$i}";
                             $this->_validateRelationModel($pettyRelationName, $relationName, $relationModel, $event);
                         }
                     }
                 }
             }
         }
         if (!$event->isValid) {
             throw new Exception("One of the related model could not be validated");
         }
     } catch (Exception $e) {
         if ($this->_transaction instanceof Transaction && $this->_transaction->isActive) {
             $this->_transaction->rollBack();
             // If anything goes wrong, transaction will be rolled back
         }
         $event->isValid = false;
         // Stop saving, something went wrong
         return false;
     }
     return true;
 }