PHP中SESSION自定义会话管理器

<?php
class CustomSession implements SessionHandlerInterface{
private $link;
private $lifetime;
public function open($savePath,$session_name){
$this->lifetime=get_cfg_var('session.gc_maxlifetime');
$this->link=mysqli_connect('localhost','root','root','session_test');
mysqli_query($this->link,"SET names UTF8");
if($this->link){
return true;
}
return false;
}
public function close(){
mysqli_close($this->link);
return true;
}
public function read($session_id){
$sql="SELECT *from sessions where session_id='{$session_id}'
and session_expires >".time();
$result=mysqli_query($this->link,$sql);
if(mysqli_num_rows($result)){
return mysqli_fetch_array($result)['session_data'];
}
return "";
}
public function write($session_id,$session_data){
$newExp=time()+$this->lifetime;
//首先查询是否存在指定的session_id,如果存在相当于更新数据，否则是第一次，则写入数据
$sql="SELECT * from sessions where session_id={'$session_id'}";
$result=mysqli_query($this->link,$sql);
if(mysqli_num_rows($result)==1){
$sql="UPDATE sessions set session_expires='{$newExp}',session_data='{$session_data}'
where session_id='{$session_id}' ";
}else{
$sql="INSERT into sessions values('{$session_id}','$session_data','{$newExp}')";
}
mysqli_query($this->link,$sql);
return mysqli_affected_rows($this->link)==1; }
public function destroy($session_id){
$sql="DELETE from sessions where session_id='{$session_id}'";
mysqli_query($this->link,$sql);
return mysqli_affected_rows($this->link)==1;
}
public function gc($maxlifetime){
$sql="DELETE from sessions where session_expires<".time();
mysqli_query($this->link,$sql);
if(mysqli_affected_rows($this->link)>0){
return true;
}
return false;
}
}

<?php
header("Content-type:text/html;charset=utf-8");
require_once 'customSession.php';
$customSession=new CustomSession();
ini_set('session.save_handler', 'user');
session_set_save_handler($customSession,true);
session_start();
$_SESSION['name']='admin';
$_SESSION['pwd']='123456';

//销毁会话，从数据库中删除
<?php
require_once 'customSession.php';
$customSession=new CustomSession();
ini_set('session.save_handler', 'user');
session_set_save_handler($customSession,true);
session_start();
session_destroy();