CREATE TABLE `sessions` (
  `sid` char(40) NOT NULL,
  `updatetime` int(20) NOT NULL,
  `data` varchar(200) NOT NULL,
  UNIQUE KEY `sid` (`sid`) USING HASH
) ENGINE=MEMORY DEFAULT CHARSET=utf8;

<?php
//引入数据库文件
include "db.php";
class MySessionHandler implements SessionHandlerInterface
{
    private $savePath;
    private $sessData;
    public $expiretime;    //设置过期时间
    public $db;    //数据库
    public function __construct($hanlder =''){
         
        $this->db = Database::getInstance();   
         
        //获取数据库实力 
        ///var_dump($this->db);
         
    }
     
    public function open($savePath, $sessionName)
    {
 
        return true;
    }
 
    public function close()
    {
        return true;
    }
 
    public function read($id)
    {    
        $sql ="select * from sessions where sid ='$id'";
        $result = $this->db->execute($sql);
            if(!empty($result)){
                 return $this->sessData = $result;
            }
    }
            //函数的参数 $id -> 当前会话ID
            //数据DATA -> 序列化之后的字符串
    public function write($id, $data)
    {
        // echo $id;
        // echo $data;
        $now = time();
        $newExp = $now+$this->expiretime;    //总时间=当前时间 + 期限时间
        $sql = "select * from sessions where sid ='$id'";
        $result = $this->db->getOne($sql);
        //var_dump($result);
        if($data==''||isset($data)){
            $data = $this->sessData;
        }
            if($result){
            //如果存在则更新
   $sql ="update sessions set updatetime = '$newExp',data ='$data' where sid = '$id'";
                //echo $sql;
                    $update_data =$this->db->execute($sql);
                    if($update_data){
                        return true;
                    }
                 
            }else{
            //不存在则生成生成
    $sql = "insert into sessions(sid,updatetime,data) values('$id','$now','$data')";
        $insert_data = $this->db->execute($sql);
        if($insert_data){
        return true;
                }
            }
            return false;
    }
 
    public function destroy($id)
    {        //销毁
        $sql = "delete from sessions where sid="."$id";
        $destory = $this->db->execute($sql);
        if($destory){
              return true;
        }else{
            return false;
        }
    }
 
    public function gc($sessMaxLifeTime)
    {
      $t = time();
    $sql ="delete from sessions where $t - 'updatetime'>${sessMaxLifeTime}";
        $data = $this->db->execute($this->tosql);
        if($data){
            return true;
        }else{
            return false;
            }
        return true;
    }
}

//判断PHP版本
 if(version_compare(PHP_VERSION,5.4)==1){
              
     session_set_save_handler($handler, true);
    session_start();
    }else{   
        ini_set('session.use_trans_sid',0);
        ini_set('session.use_cookies',1);
        ini_set('session.cookie_path','/');
            ini_set('session.save_handler','user');
            session_module_name('user');
            session_set_save_handler(array($session,"open"),array($session,"close"),array($session,"read"),array($session,"write"),array($session,"destory"),array($session,"gc"));
            session_start();     
         }
$_SESSION['QQ']="QQ";
echo $_SESSION['QQ'];

<?php 
class Database{
         static $instance;
        static $db;
    static  function getInstance(){      
        if(self::$instance){
            return self::$instance;
        }else{
            return new  Database();   
        }
    }
    public function __construct(){
        self::$db = new PDO('mysql:host=localhost;dbname=session', 'root','');
    }
 
        public  function getOne($sql){
            $rs =self::$db->query($sql);
            @$rs->setFetchMode(PDO::FETCH_ASSOC);//返回关联数组
            $result = $rs -> fetch();
            return $result;
        }
        public function execute($sql){
             
             
                $rs = self::$db->exec($sql);
                return $rs;
                 
        } 
     
 
}
 
 
//$data = Database::getInstance();
//var_dump($data);

<?php
class SessionManager{
    private $redis;
    private $sessionSavePath;
    private $sessionName;
    private $sessionExpireTime = 30;
    public function __construct(){
        $this->redis = new Redis();
        $this->redis->connect('127.0.0.1',6379);    //连接redis
        $retval = session_set_save_handler(
            array($this,"open"),
            array($this,"close"),
            array($this,"read"),
            array($this,"write"),
            array($this,"destory"),
            array($this,"gc")
        );
            session_start();
    }
     
        public function open($path,$name){
            return true;
        }
        public function close(){
            return true;
        }
        public function read($id){
            $value = $this->redis->get($id);
            if($value){
                return $value;
            }else{
                return "";
            }
        }
        public function write($id,$data){
            if($this->redis->set($id,$data)){
                $this->redis->expire($id,$this->sessionExpireTime);  
                  //设置过期时间
                return true;
            }
            return false;
        }
        public function destory($id){
            if($this->redis->delete($id)){
                return true;
            }
            return false;
        }
        public function gc($maxlifetime){
            return true;
        }
        //析构函数
        public function __destruct(){
            session_write_close();
        }
         
}
 
 
$re = new SessionManager();
$_SESSION['name'] = "qq";
echo $_SESSION['name'];