PHP会话不能与I.E浏览器一起使用

I have this code to ensure user "agree" to the agreement before going to other pages of the domain

$agreement_check = $_SESSION['agreement'];
$current_path = $_SERVER['REQUEST_URI'];


if($agreement_check!="yes" && (!strstr($current_path,"/agree/")) )
{
if(!header("Location: " . $domainURL . "login"))
    { die("Agreement check expire."); }
}


There 2 buttons in this /agree page

1 is Agree, another is Disagree

if($final_check=="yes")
{
$_SESSION['agreement'] = "yes";
if(!header('Location: ' . $domainURL))
{
die('Server Error.');
}
}

And if agree, the page will set

$_SESSION['agreement'] = "yes";

else it will redirect to homepage

For disagree, it will redirect to login page.

The question is

I used Firefox, Chrome & I.E for this test case, all works.

But some of my visitors , I not sure their I.E version, when they click on agree, the server redirect them out of the site.

I think they din't pass this check

$agreement_check = $_SESSION['agreement'];
$current_path = $_SERVER['REQUEST_URI'];


if($agreement_check!="yes" && (!strstr($current_path,"/agree/")) )
{
if(!header("Location: " . $domainURL . "login"))
    { die("Agreement check expire."); }
}

What could it be that I do wrong in this code. Their I.E version could be I.E 8 or earlier