How to Use in jQuery the PHP session variable set by Ajax.

How to Use in jQuery the PHP session variable set by Ajax.

As for two general PHP files, no big deal to use the session variable if 'session_start()' is declared at the top.

session_start();
$_SESSION['name'];

---------------------------------------

But in jQuery, how should I use the session in index.php?
The var name doesn't work at the end of codes.
 
[index.php]-------------------------------------------------------------------------------------
<?php
session_start();
}
?>
<!DOCTYPE html>
<html>
<head>
bla bla

<script type="text/javascript">           
$(document).ready(function () {

$('#login').click(function(){

                bla bla~
                                                      
                    $.ajax({
           type: 'POST',
           url: ' signin_process.php', / /$_SESSION['user_id'] is set;
           data: jdata
                       
       })
       .done(function(data){
       
                 
       }) //ajax
  }//

var name;
name= "<?php echo $_SESSION['user_id'];?>";


   }); //$('#login').