Db::error PHP Method

    public function error()
    {
        // $this->error = mysql_error($this->_linkID);
        if ($this->debug && '' != $this->queryStr) {
            $this->error .= "\n [ SQL语句 ] : " . $this->queryStr;
        }
        return $this->error;
    }

 public function save()
 {
     if (is_numeric($this->page_id) && is_string($this->page_name)) {
         $db = new Db();
         $id = $db->quote($this->page_id);
         $category_id = $db->quote($this->category_id);
         $name = $db->quote($this->page_name);
         $url = $db->quote($this->url);
         $top_description = $db->quote($this->top_description);
         $bottem_description = $db->quote($this->bottom_description);
         $keyword = $db->quote($this->keyword);
         $title = $db->quote($this->title);
         $description = $db->quote($this->description);
         $access_type = $db->quote($this->access_type);
         $active = $db->quote($this->page_status);
         $author = $db->quote(1);
         $modified = $db->quote(1);
         $query = "INSERT INTO " . $this->tableName() . " (page_id, category_id, name, url, top_description, bottem_description, \n                Keyword, title, description, author, modified_by, access_type,  active) \n                VALUES({$id}, {$category_id},  {$name}, {$url}, {$top_description}, {$bottem_description}, {$keyword}, {$title}, {$description},\n                    {$author}, {$modified}, {$access_type}, {$active})\n                ON DUPLICATE KEY UPDATE    \n                name= {$name}, category_id={$category_id}, url={$url},top_description={$top_description}, bottem_description={$bottem_description}, \n                Keyword={$keyword}, title={$title}, description={$description}, author={$author}, modified_by={$modified}, \n                   active={$active}, access_type={$access_type}";
         if ($db->query($query)) {
             return true;
         } else {
             Error::set($db->error());
         }
     }
     return false;
 }