PHP会话登录在同一服务器上的站点之间交叉

I have CentOS LAMP with multiple sites. I use PHP session variable for the log into the wesites. My problem is if you log into one site you can open another site on the same server and you will be logged in. The sites are completely separate so I want them to have to log into each separately. Each site has a different user DB.I have CentOS LAMP with multiple sites. I use P