在tomcat关闭后，Session仍然保持价值

I am using XAMPP app for my server. in my page: I write code for update session value as below

<?php
session_start();
$start = isset($_SESSION['start']) ? $_SESSION['start'] : 0; 
$_SESSION['start'] = $start + $num;
?>   

I run server in long time, after that I shutdown XAMPP with apache service after I restart apache again, I see that session value still keep ?