/**
  * @param $son          HTMLTableCell object
  * @param $sons_header  HTMLTableHeader object
  **/
 function addSon(HTMLTableCell $son, HTMLTableHeader $sons_header)
 {
     if (!isset($this->sons[$sons_header->getName()])) {
         $this->sons[$sons_header->getName()] = array();
     }
     $this->sons[$sons_header->getName()][] = $son;
 }
 function getHeaderAndSubHeaderName(&$header_name, &$subheader_name)
 {
     $header_name = $this->header->getName();
     $subheader_name = parent::getName();
 }