db_config = pc_base::load_config('database');
		$this->header = "<\x3Fxml version=\"1.0\" encoding=\"UTF-8\"\x3F>\n\t";
	    $this->charset = "UTF-8";
	    $this->footer = "\t\n";
	    $this->items = array();
		parent::__construct();
	}
	/**
     * 增加一个新的子项
     *@access   public
     *@param    google_sitemap  item    $new_item
     */
    function add_item($new_item) {
    	 $this->items[] = $new_item;
    }
    
	/**
     * 生成XML文档
     *@access    public
     *@param     string  $file_name  如果提供了文件名则生成文件,否则返回字符串.
     *@return [void|string]
     */
    function build( $file_name = null ) {
    	
        $map = $this->header . "\n";
        foreach ($this->items AS $item) { 
            $map .= "\t\t\n\t\t\t$item->loc\n";
            // lastmod
            if ( !empty( $item->lastmod ) )
                $map .= "\t\t\t$item->lastmod\n";
            // changefreq
            if ( !empty( $item->changefreq ) )
                $map .= "\t\t\t$item->changefreq\n";
            // priority
            if ( !empty( $item->priority ) )
                $map .= "\t\t\t$item->priority\n";
            $map .= "\t\t\n\n";
        }
        $map .= $this->footer . "\n";
        if (!is_null($file_name))
        {
            return file_put_contents($file_name, $map);
        }
        else
        {
            return $map;
        }
    }
	
}
?>