code: protected function buildValues()/*# : array */
      {
          $result = [];
          $cols = array_keys($this->clause_set);
  
          $maxRow = count($this->clause_data) - 1;
          foreach ($this->clause_data as $num => $row) {
              $values = [];
              foreach ($cols as $col) {
                  if (isset($row[$col])) {
                      $values[] = $this->processValue($row[$col]);
                  } else {
                      $values[] = $this->getSettings()['useNullAsDefault'] ?
                          'NULL' : 'DEFAULT';
                  }
              }
              $result[] = '(' . join(', ', $values) . ')' . ($num !== $maxRow ?
                  ',' : '');
          }
  
          return $result;
      }
docs: Build VALUES ( ... )
  
  @return array
  @access protected