IE 9 and below will not load the entire page. I have found that this happens when it meets the following line of PHP code:
if(isset($_POST['nextstep'])){
The post itself is rather large, 288 lines to be exact.
Again this problem only occurs in IE.
If there is anything you need from me let me know.
--------------- EDIT ---------------- !! SOLVED !!
I found that it was not in fact the $_POST, well it was, as it would fine without it. It was in-fact a meta refresh problem.
echo '<meta http-equiv="refresh" content="0;url=index.php">';
This was the line that actually caused the problem, the page would successfully complete the server side requests, however when the browser came to this echo it would stop.
I also tried some JS to force re-direct like:
window.location.href = window.location.pathname = "index.php";
In the end I solved it by re-directing via PHP.
header("Location: index.php");
Hope this helps anyone in the future that encounters this problem with meta refreshes.
As this is your server side it's not dependent on your PHP code. perhaps you've somehow hit an infinite loops somewhere, without more of the source code it'll be nearly impossible to provide any valuable insight.