php mysql数据库操作分页类

        var $url;
        var $table;
        var $new_sql;        //指定的SQL语句
        var $db;
        function __construct(){
            global $db;
            $this->db = $db;
            $tmp_page = intval(trim($_GET["page"]));
            $this->page = empty($tmp_page)?1:$tmp_page;
            $this->set_table();
            $this->page_size = 20;
            $this->num_btn    = 9;
            $this->img_path    = '/images/';
            $this->img        = array("ico_first.gif", "ico_front.gif", "ico_next.gif", "ico_last.gif");
        }
        function set_table(){
            $this->table["tablename"]    = "";
            $this->table["id"]        = "id";
            $this->table["orderby"]    = $this->table["id"];
            $this->table["descasc"]    = "DESC";
            $this->table["fileds"]    = "*";
            $this->table["where"]    = "";
        }
        function set_img(){
            $this->img_btn[0]    = "<img src='".$this->img_path.$this->img[0]."' alt='首页' border='0' align='absmiddle'/>";
            $this->img_btn[1]    = "<img src='".$this->img_path.$this->img[1]."' alt='上一页' border='0' align='absmiddle'/>";