自定义session处理机制之数据库存储session

自定义session处理机制主要由session_set_save_handler()函数实现。注意参数的顺序

首先在数据库中建立session表

CREATE TABLE `session` (
  `sid` char(32) NOT NULL DEFAULT "",
  `data` varchar(255) NOT NULL DEFAULT "",
  `mtime` int(10) NOT NULL DEFAULT "0",
  `ip` char(15) NOT NULL DEFAULT "",
  `card` char(32) NOT NULL DEFAULT ""    //该项主要存储用户的ip、浏览器信息等，用来判断用户的sessionid是否合法，以防止用户sessionid被劫持后伪造用户登录
) ENGINE=MyISAM DEFAULT CHARSET=gbk

<?php
class session{
	protected $conn;
	protected $card;
	protected $max_time;
	protected $table;
	public function __construct(){
		if(ini_get("session.save_handler")=="user" || ini_set("session.save_handler", "user")){
			session_set_save_handler(
				array($this,"start"),
				array($this,"close"),
				array($this,"read"),
				array($this,"write"),
				array($this,"destroy"),
				array($this,"gc")
				);
			$this->conn=mysql_connect("localhost","root","root") or die("连接错误！");
			mysql_select_db("test");
			$this->table="session";
			$this->max_time=100;
			$this->card=md5($_SERVER["REMOTE_ADDR"].$_SERVER["HTTP_USER_AGENT"]);
			session_start();
		}
	}
	public function start($path,$sess_name){
		echo "start</br>";
	}
	public function read($sid){
		$sql="select `data` from `".$this->table."` where `sid`="{$sid}" and data="".$this->card.""";
		// echo $sql;
		$result=mysql_query($sql);
		$row=mysql_fetch_assoc($result);
		echo "read</br>";
		return mysql_affected_rows()>0 ? $row["data"]:"";
	}
	public function write($sid,$data){
		// $sql="update "
		$sql  = "select `sid` from ".$this->table." where `sid` ="{$sid}" and `card`="".$this->card.""";  
		mysql_query($sql);
		$time=time();
		if(mysql_affected_rows()>0){
			$sql="update `".$this->table."` set `data`="{$data}",`mtime`={$time} where `sid`="{$sid}"";
			echo $sql;
		}else{
			$sql="insert into ".$this->table." (`sid`,`data`,`mtime`,`ip`,`card`) values ("{$sid}","{$data}","{$time}","{$_SERVER["REMOTE_ADDR"]}","".$this->card."")";
		}
		echo "write</br>";
		return mysql_query($sql)?true:false;
	}
	public function close(){
		self::gc($this->max_time);
		echo "close</br>";
		mysql_close($this->conn);
		return true;
	}
	public function destroy($sid){
		$sql="delete from ".$this->table." where `sid`="{$sid}"";
		mysql_query($sql);
		return true;
	}
	public function gc($max_time){
		$max_time=$this->max_time;
		$time=time();
		$sql="delete from ".$this->table." where `mtime`<".($time-$max_time);
		mysql_query($sql);
		echo "gc</br>";
		return true;
	}
}
$session=new session();
$_SESSION["username"]="zhangsan";
$_SESSION["age"]=20;