kartik\grid\controllers\ExportController::actionDownload PHP Method

    public function actionDownload()
    {
        $request = Yii::$app->request;
        $type = $request->post('export_filetype', 'html');
        $name = $request->post('export_filename', Yii::t('kvgrid', 'export'));
        $content = $request->post('export_content', Yii::t('kvgrid', 'No data found'));
        $mime = $request->post('export_mime', 'text/plain');
        $encoding = $request->post('export_encoding', 'utf-8');
        $bom = $request->post('export_bom', true);
        $config = $request->post('export_config', '{}');
        if ($type == GridView::PDF) {
            $config = Json::decode($config);
            $this->generatePDF($content, "{$name}.pdf", $config);
            /** @noinspection PhpInconsistentReturnPointsInspection */
            return;
        } elseif ($type == GridView::HTML) {
            $content = HtmlPurifier::process($content);
        } elseif ($type == GridView::CSV || $type == GridView::TEXT) {
            if ($encoding != 'utf-8') {
                $content = mb_convert_encoding($content, $encoding, 'utf-8');
            } elseif ($bom) {
                $content = chr(239) . chr(187) . chr(191) . $content;
                // add BOM
            }
        }
        $this->setHttpHeaders($type, $name, $mime, $encoding);
        return $content;
    }