session入mysql

<?php
ini_set("session.save_handler","user");
//session.gc_probability = 1 分子
ini_set("session.gc_probability",1);
//session.gc_divisor = 1000 分母
ini_set("session.gc_divisor",2);
//session.gc_maxlifetime = 1440 垃圾回收时间，session有效期
session_set_save_handler( "open","close","read","write","destroy","gc" );
//连接数据库
function open(){
@$link = mysql_connect('127.0.0.1', 'root', 'root');
mysql_query('set names utf8');
mysql_query('use wangbin');
}
function close(){
mysql_close();
}
function read($sess_id){
$sql = "select session_data from `session` where session_id = '$sess_id'";
$result = mysql_query($sql);
if($rows = mysql_fetch_assoc($result)){
return $rows['session_data']; }
else{
return '';
}
}
function write($sess_id,$sess_data){
$sql = "insert into `session` (session_id,session_data,session_time) values('$sess_id','$sess_data', now()) on duplicate key update session_data = '$sess_data' , session_time = now()";  //这是为了gc()
return mysql_query($sql);

}
function destroy($sess_id){
echo __FUNCTION__;
$sql = "delete from `session` where session_id = '$sess_id'";
return mysql_query($sql);

}
function gc($sess_id){
$maxlifetime = ini_set("session.gc_maxlifetime");
echo __FUNCTION__;
$sql = "delete from `session` where now()-session_time > '$maxlifetime' ";
return mysql_query($sql);
}
header("content-type:text/html;charset=utf8");
session_start();
$_SESSION['name']='aa';
//echo session_id();
echo $_SESSION['name'];