yii\data\DataProviderInterface::getTotalCount PHP Method

    public function getTotalCount();

 /**
  * Serializes a data provider.
  * @param DataProviderInterface $dataProvider
  * @return array the array representation of the data provider.
  */
 protected function serializeDataProvider($dataProvider)
 {
     $models = $this->serializeModels($dataProvider->getModels());
     if ($dataProvider->getPagination() === false) {
         return $models;
     } else {
         return ['total' => $dataProvider->getTotalCount(), 'rows' => $models];
     }
 }