Jquery. IE does not see the value from $_SESSION. How to win?

Question

PHP

Does not work in IE 9, 10, 11. Works in
FF and Chrome.

On the main page I set $_SESSION["step"] = 1
On the button I send $.post
After $.post the page is reloaded.

$.post('/', {catalog: 'setstep'}, function(e){
            window.location = e;
});

PHP sets $_SESSION["step"] = 2

Smarty draws hmtl based on $_SESSION["step"] value

{if $smarty.session.step == 1} 
<div id="1">1</div>
{else}
<div id="2">2</div>

Appears in browsers, remains in IE <div id=1>, and the value of $_SESSION["step"] == 2 (displayed via echo).
If you press the button a second time, IE will open page c <div id="2">
. Tried to send different headers, it doesn't help.

$.ajaxSetup({
    cache: false,
    dataType: 'text',
        contentType: "application/x-www-form-urlencoded; charset=utf-8"
  });

Answer 1

If a reboot is made after the post, then what is the scary sense of making it a javascript?
Do it humanly, HTTP post - HTTP redirect - and everything will work for you.

Answer 2

Apparently in order for the clock to spin on the screen until the result is returned. PHP has a lot going on at this time.

Answer 3

session_write_close() add somewhere at the end of the script