function show($page_no)
    {
        //計(jì)算分頁數(shù)
        $record_count=$this->db->count_all('t_message');
        $page_count= Floor(($record_count-1)/PAGE_SIZE);
        if($page_count<0)
            $page_count=0;
        
        //查詢當(dāng)前頁面留言
        $this->db->order_by("id", "desc");
        $query = $this->db->get('t_message', 10, 10*$page_no);

        //將前臺需要的數(shù)據(jù)裝配成數(shù)組
        $arr = array(
              //當(dāng)前頁面號
            'current_no' => "{$page_no}" ,
            'page_count' =>"{$page_count}" ,
            'record_count' =>"{$record_count}" ,
            //下面字段保存10條留言信息，包括username , content, time
            'message' => $query->result_array()
        );
        $json_string=$this->json->encode($arr);
        echo  $json_string;    
    }