I use wampserver2.1 php5.3.3, I found session_regenerate_id(true) not work in my script,document says when I set the parameter 'delete_old_sessions' true, there should be a new sid and all the session variables should be deleted, but the fact is after the function, $_session[abc] is still there. did I misunderstand the function,what is my problem? I appreciate if anyone can help me, <?php session_start(); $_SESSION['abc']=12323; session_regenerate_id(true); echo $_SESSION['abc']; ?> I thought it should display none, but it outputs:12323