function __construct($id, $table_name)
 {
     parent::__construct($table_name);
     $this->sql = "SELECT * FROM `" . $table_name . "` WHERE `news_id`=" . $id;
 }
<?php

require "data_operate.php";
if ($_REQUEST['operate_type'] === "select") {
    //创建操作对象
    $request = new connect_query($_REQUEST['table_name']);
    //连接数据库
    $request->connect_database();
    //查询并返回最新状态
    echo $request->select_new_data();
    //关闭数据库连接
    $request->close();
}