重定向页面并使用ajax发送var值

I redirect to page star.php using

window.location.href = 'start.php';

Before I redirect I just want to send(post) var userid to start.php

how could I do?

you can not post like this. Instead pass it through url like:

window.location.href = 'start.php?userid='+userid;

and you will get the value as $_GET['userid'] in start.php