<?php
  /*
  *@author  Fahy
  *數(shù)據(jù)庫為mysql，
  *數(shù)據(jù)庫名為session，表名為session，
  *表中字段包括PHPSESSID,update_time,client_ip,data
  */
  class Session{
    private static $handler = null;
    private static $ip = null;
    private static $lifetime = null;
    private static $time = null;
    
    //配置靜態(tài)變量
    private static function init($handler){
      self::$handler = $handler;    //獲取數(shù)據(jù)庫資源
      self::$ip = !empty($_SERVER["REMOTE_ADDR"])? $_SERVER["REMOTE_ADDR"]:'unkonw';    //獲取客戶端ip
      self::$lifetime = ini_get('session.gc_maxlifetime');    //獲取session生命周期
      self::$time = time();    //獲取當前時間
    }
    //調用session_set_save_handler()函數(shù)并開啟session
    static function start($pdo){
      self::init($pdo);
      session_set_save_handler(
        array(__CLASS__,'open'),
        array(__CLASS__,'close'),
        array(__CLASS__,'read'),
        array(__CLASS__,'write'),
        array(__CLASS__,'destroy'),
        array(__CLASS__,'gc')
      );
      session_start();
    }
    
    public static function open($path,$name){
      return true;
    }
    public static function close(){
      return true;
    }
    
    //查詢數(shù)據(jù)庫中的數(shù)據(jù)
    public static function read($PHPSESSID){
      $sql = "select PHPSESSID,update_time,client_ip,data from session where PHPSESSID=?";
      $stmt = self::$handler->prepare($sql);
      $stmt->execute(array($PHPSESSID));
      if(!$result = $stmt->fetch(PDO::FETCH_ASSOC)){
        return '';
      }
      if(self::$ip == $result['client_ip']){
        self::destroy($PHPSESSID);
        return '';
      }
      if(($result['update_time']+self::$lifetime)<self::$time){
        self::destroy($PHPSESSID);
        return '';
      }
      return $result['data'];
    }
    /*
    *首先查詢該session是否存在數(shù)據(jù)，如果存在，則更新數(shù)據(jù)，如果不存在，則插入數(shù)據(jù)
    */
    //將session寫入數(shù)據(jù)庫中，$data傳入session中的keys和values數(shù)組
    public static function write($PHPSESSID,$data){
      $sql = "select PHPSESSID,update_time,client_ip,data from session where PHPSESSID=?";
      $stmt = self::$handler->prepare($sql);
      $stmt->execute(array($PHPSESSID));
      
      if($result=$stmt->fetch(PDO::FETCH_ASSOC)){        
        if($result['data'] != $data || self::$time > ($result['update_time']+30)){
          $sql = "update session set update_time=?,data=? where PHPSESSID = ?";
          $stmt = self::$handler->prepare($sql);
          $stmt->execute(array($self::$time,$data,$PHPSESSID));
        }
      }else{
        if(!empty($data)){
          try{
            $sql = "insert into session(PHPSESSID,update_time,client_ip,data) values(?,?,?,?)";
          }catch(PDOException $e){
            echo $e->getMessage();
          }
          $sth = self::$handler->prepare($sql);
          $sth->execute(array($PHPSESSID,self::$time,self::$ip,$data));
        }
      }
      return true;
    }
    
    public static function destroy($PHPSESSID){
      $sql = "delete from session where PHPSESSID = ?";
      $stmt = self::$handler->prepare($sql);
      $stmt->execute(array($PHPSESSID));
      return true;
    }
    public static function gc($lifetime){
      $sql = "delete from session where update_time<?";
      $stmt = self::$handler->prepare($sql);
      $stmt->execute(array(self::$time-$lifetime));
      return true;
    }
  }
  //使用PDO連接數(shù)據(jù)庫
  try{
    $pdo = new PDO("mysql:host=localhost;dbname=session","root","hwj193");
  }catch(PDOException $e){
    echo $e->getMessage();
  }
  //傳遞數(shù)據(jù)庫資源
  Session::start($pdo);