code: private function writeRelationship(XMLWriter $objWriter, $pId, $pType, $pTarget, $pTargetMode = '')
      {
          if ($pType != '' && $pTarget != '') {
              // Write relationship
              $objWriter->startElement('Relationship');
              $objWriter->writeAttribute('Id', 'rId' . $pId);
              $objWriter->writeAttribute('Type', $pType);
              $objWriter->writeAttribute('Target', $pTarget);
  
              if ($pTargetMode != '') {
                  $objWriter->writeAttribute('TargetMode', $pTargetMode);
              }
  
              $objWriter->endElement();
          } else {
              throw new WriterException('Invalid parameters passed.');
          }
      }
docs: Write Override content type.
  
  @param XMLWriter $objWriter XML Writer
  @param int $pId Relationship ID. rId will be prepended!
  @param string $pType Relationship type
  @param string $pTarget Relationship target
  @param string $pTargetMode Relationship target mode
  
  @throws WriterException