<?php
namespace Lib;
class Session{
 private $mypdo;
 public function __construct() {
 session_set_save_handler(
 [$this,'open'],
 [$this,'close'],
 [$this,'read'],
 [$this,'write'],
 [$this,'destroy'],
 [$this,'gc']
 );
 session_start();
 }
 public function open() {
 $this->mypdo= \Core\MyPDO::getInstance($GLOBALS['config']['database']);
 return true;
 }
 //关闭会话
 public function close() {
 return true;
 }
 //读取会话
 public function read($sess_id) {
 $sql="select sess_value from sess where sess_id='$sess_id'";
 return (string)$this->mypdo->fetchColumn($sql);
 }
 //写入会话
 public function write($sess_id,$sess_value) {
 $sql="insert into sess values ('$sess_id','$sess_value',unix_timestamp()) on duplicate key update sess_value='$sess_value',sess_time=unix_timestamp()";
 return $this->mypdo->exec($sql)!==false;
 }
 //销毁会话
 public function destroy($sess_id) {
 $sql="delete from sess where sess_id='$sess_id'";
 return $this->mypdo->exec($sql)!==false;
 }
 //垃圾回收
 public function gc($lifetime) {
 $expires=time()-$lifetime;	//过期时间点
 $sql="delete from sess where sess_time<$expires";
 return $this->mypdo->exec($sql)!==false;
 }
}