code: private function writeStringRecord($stringValue)
      {
          $record = 0x0207; // Record identifier
          $data = StringHelper::UTF8toBIFF8UnicodeLong($stringValue);
  
          $length = strlen($data);
          $header = pack('vv', $record, $length);
  
          $this->append($header . $data);
      }
docs: Write a STRING record. This.
  
  @param string $stringValue