code: private function writeFooter()
      {
          $record = 0x0015; // Record identifier
  
          /* removing for now
          // need to fix character count (multibyte!)
          if (strlen($this->phpSheet->getHeaderFooter()->getOddFooter()) <= 255) {
              $str = $this->phpSheet->getHeaderFooter()->getOddFooter();
          } else {
              $str = '';
          }
          */
  
          $recordData = StringHelper::UTF8toBIFF8UnicodeLong($this->phpSheet->getHeaderFooter()->getOddFooter());
          $length = strlen($recordData);
  
          $header = pack('vv', $record, $length);
  
          $this->append($header . $recordData);
      }
docs: Store the footer caption BIFF record.