yupe\components\ContentType::setHeader PHP Method

    public static function setHeader($contentTypeId)
    {
        if (!is_null(self::getHeader($contentTypeId))) {
            header(self::getHeader($contentTypeId));
            return true;
        } else {
            return false;
        }
    }

 public function actionView($id)
 {
     $model = Export::model()->findByPk($id);
     if (false === $model) {
         throw new CHttpException(404);
     }
     $criteria = new CDbCriteria();
     $criteria->compare('t.status', Product::STATUS_ACTIVE);
     if (!empty($model->categories)) {
         $criteria->addInCondition('t.category_id', (array) $model->categories);
     }
     if (!empty($model->brands)) {
         $criteria->addInCondition('t.producer_id', (array) $model->brands);
     }
     $dataProvider = new CActiveDataProvider('Product', ['criteria' => $criteria]);
     $offers = new CDataProviderIterator($dataProvider, 100);
     ContentType::setHeader(ContentType::TYPE_XML);
     $this->renderPartial('view', ['model' => $model, 'currencies' => Yii::app()->getModule('store')->getCurrencyList(), 'categories' => StoreCategory::model()->published()->findAll(), 'offers' => $offers]);
 }