public function getAllURLs()
  {
    $URLs = array();
    
    @reset($this->urls);
    while (list($pri_lvl) = @each($this->urls))
    {
      $cnt = count($this->urls[$pri_lvl]);
      for ($x=0; $x<$cnt; $x++)
      {
        $URLs[] = &$this->urls[$pri_lvl][$x];
      }
    }
    
    return $URLs;
  }