yii\web\Response::sendContent PHP Method

    protected function sendContent()
    {
        if ($this->stream === null) {
            echo $this->content;
            return;
        }
        set_time_limit(0);
        // Reset time limit for big files
        $chunkSize = 8 * 1024 * 1024;
        // 8MB per chunk
        if (is_array($this->stream)) {
            list($handle, $begin, $end) = $this->stream;
            fseek($handle, $begin);
            while (!feof($handle) && ($pos = ftell($handle)) <= $end) {
                if ($pos + $chunkSize > $end) {
                    $chunkSize = $end - $pos + 1;
                }
                echo fread($handle, $chunkSize);
                flush();
                // Free up memory. Otherwise large files will trigger PHP's memory limit.
            }
            fclose($handle);
        } else {
            while (!feof($this->stream)) {
                echo fread($this->stream, $chunkSize);
                flush();
            }
            fclose($this->stream);
        }
    }

 public function sendContent()
 {
     if ($this->stream === null) {
         $this->content = Yii::$app->getI18n()->removeLegacyLangTags($this->content);
     }
     parent::sendContent();
 }