Passing a $_SESSION failed when creating the $_SESSION within Ajax function - php

Question

I have a simple registration form and the new comers will be registered with an ajax function. There I create a $_SESSION['is_logged'] when the registration is finished.
On var_dumb I get that the var is set. But when redirect on another page it is empty (I have included already the session_start() on the both pages...
I have read somewhere in the net that:
"Sessions are ONLY written on a page load/refresh".
Is this the case, or I have to look for some other issues within my code.
the ajax:
$.ajax({
url:"../controllers/register.php",
type:"POST",
data:res,
success: function(responce){
if (responce==1) {
$('#msg').addClass('msg-warning');
$("#form").css('display',"none");
$('#msg').append("<p>It seems that you have already submited the form. Click to "+
" <a href='login.php'>log-in</a> or to <a href='register.php'>register</a>.</p>");
}
else if (responce==2) {
$('#msg').addClass('msg-warning');
$("#form").css('display',"none");
$('#msg').append("<p>You have successfully created account. Click to "+
" <a href='start.php'>welcome</a> to start your .</p>");
$('.menu').append("<li><a href='logout.php'>Log out</a></li>")
}
else{
$('#msg').text(responce);
}
},
error: function(){
$('#msg').text("Opss, try again");
}
});
the register.php file:
if (isset($_SESSION['submited'])) {
echo 1;
exit;
}
include_once('../models/functions.php');
// Give the post parametters to another var
$arr=$_POST;
// function for uploading
$reg = registerMe($arr);
if ($reg === true) {
$_SESSION['submited']=1;
$_SESSION['is_logged']=1
echo(2);
}
else{
echo($reg);
}
exit;
The session_start(); is included in the header of the first page where from the ajax is started.And the second page - where the $_SESSION['is_logged'] is lost, again the session_start(); is part of dc_header(); function. start.php:
<?php
dc_header("Речник|Регистрация");
if (!isset($_SESSION['is_logged'])) {
#header("location: ../views/login.php");
var_dump($_SESSION);
}
?>

Answer 1

add
session_start();
to the top of register.php
You need to specify session_start, so your server who was commanded to execute "register.php" (either from ajax, direct call, browser scripts, cron job or whatever possible you-name-it) will handle the execution and the setting of $_SESSION variables in reference to the connected clients session. Server won't guess by itself that this is an "ajax call from an already session_start page". You need to specify that whatever is done in register.php is done in the current client's session.