I'm trying to write the logout of a website. When I do this I want the page to redirect to the login page. I think I'm doing it the correct way, but can't get the right result. Could you guys point me in the right direction?

Relevant Code:

<button onclick="logout()">Logout</button>

function logout()
{
var xmlhttp;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.location=xmlhttp.responseText;
}
}
xmlhttp.open("GET","logout.php",true);
xmlhttp.send();
}

<?php
session_destroy();

header("Location:http://localhost:8888/loginns.html");

mysql_close($con);
?>

Thanks!