Session fails to maintain after page redirect - php

Question

I have been beating my my head over this. My code is virtually identical to other projects where this DOES work. Here is how I do it:
session_start();
set_up_session($username);
redirect_to('index.php');
And the two functions:
function redirect_to($location=null) {
if($location!=null) {
header("Location: {$location}");
exit;
}
}
function set_up_session($username) {
session_start();
$_SESSION['user_id']=$id;
$_SESSION['logged_in']=true;
$_SESSION['username']=$username;
}
if I comment out the redirect and echo any of the $_SESSION var's, the var reads correctly. But after the redirect, the session ends.
This is what's on the next page.
<?php if (!isset($_SESSION['logged_in'])) { ?>
// do stuff <-- this is what gets shown showing session is no longer active
<?php } else { ?>
<p>Hi, <?php echo $_SESSION['username']; ?></p>
<?php } ?>

Answer 1

make sure the page you are redirecting to has session_start() at the top of the document
if(!isset($_SESSION)){
session_start();
}

Answer 2

My first step I would do is try this on the next page:
<?php
if (isset($_SESSION['logged_in'])) {
echo $_SESSION['username'];
} else {
//do stuff
}
?>
I had a problem a posted earlier in dealing with sessions. My resolution to the problem was to set a $_SESSION[]; to a variable. EX:
<?php
$Username = "Guest"; //Set your variable before you actually need it. (This is what fixed my problem)
if (isset($_SESSION['logged_in'])) {
$Username = $_SESSION['username'];
}
?>
NOTE: You might want to change the if (isset($_SESSION['logged_in'])) to instead check for if the username is set. For example:
<?php
$User = "Guest";
if (isset($_SESSION['username'])) {
$User = $_SESSION['username'];
} else {
//do stuff
}
?>
Also, as stated by the other user, make sure the page you redirect to has a session_start(); function in it. Otherwise, this will not work.