code: private function writeDefcol()
      {
          $defaultColWidth = 8;
  
          $record = 0x0055; // Record identifier
          $length = 0x0002; // Number of bytes to follow
  
          $header = pack('vv', $record, $length);
          $data = pack('v', $defaultColWidth);
          $this->append($header . $data);
      }
docs: Write BIFF record DEFCOLWIDTH if COLINFO records are in use.