【上海校区】session入库以及php高版本下session入库报错的解... - 黑马程序员技术交流社区

<?php
      //连接数据库
      function conn(){
            $link=mysqli_connect('localhost','root','aa','php1',3306);
         mysqli_set_charset($link,'utf8');
         return true;
      }

      function open(){
            return conn();
      }

      function close(){
            return true;
      }

      function read($sess_id){
            global $link;
            $sql = "select sess_value from sess where sess_id='{$sess_id}'";
            $res=mysqli_query($link,$sql);
            if(mysqli_fetch_row($res)[0]){
                     return mysqli_fetch_row($res)[0];
            }
            return '';
      }

      function write($sess_id,$sess_value){
            global $link;
            $time=time();
            $sql="insert into sess values('{$sess_id}','{$sess_value}','{$time}')
            on duplicate key update sess_value='{$sess_value}',sess_time='{$time}'";
            return mysqli_query($link,$sql);
      }

      function delete($sess_id){
            global $link;
            $sql="delete from sess where sess_id='{$sess_id}'";
            return mysqli_query($link,$sql);
      }

      function gc($lifetime){
            global $link;
            $nowtime=time();
            $time=$nowtime-$lifetime;
            $sql="delete from sess where sess_time<'{$time}'";
            return mysqli_query($link,$sql);
      }

      session_set_save_handler('open','close','read','write','delete','gc');
      session_start();
      $_SESSION['name']="北京";
运行一切正常，可是一旦切换到高版本，例如7.2下，就会报错，Warning: session_start(): Failed to read session data: user (path: ) 或者是其他莫名的错，解决办法也很简单，只需要在read方法里面的return mysqli_fetch_row($res)[0]，在返回之前做一下强制类型转换即可，即改成return (string)mysqli_fetch_row($res)[0];但是没强制转换之前也是字符串，为什么就不行呢？嘿嘿，你如果到传智来，我就告诉你。