PHP $_SESSION variable not working first time - php

Question

$_SESSION['isloggedin'] doesn't seem to be working on first load.
This only happens on server, not on localhost.
session_start() is at the top of each page.
initialized to: $_SESSION['isloggedin'] = false;
When user logs in $_SESSION['isloggedin'] = true;
When user logs out $_SESSION['isloggedin'] = false;
on home.php:
if (!$_SESSION['isloggedin']) {
die(header("Location: login.php"));
}
on login.php:
if ($_SESSION['isloggedin']) {
die(header("Location: home.php"));
}
When you login and sent to the home page $_SESSION['isloggedin'] doesn't seem to be true so it redirects to login.php. But since it is true it redirects to Home.php causing a redirect loop.
when a redirect loop error pops up, I refresh and am taken to the right page. Sometimes the page self refreshes and takes me to the correct page, still showing redirect error before.
Why isn't $_SESSION variable working properly on server? The correct value doesn't seem to register the first time on every page, every site link.
EDIT:
everything works as expected on localhost just not on the online server.
when login is clicked and everything passes the class login function is called:
class users {
$_SESSION['isLoggedIn'] = false;
function __construct() {
if (session_id() == "") {
session_start();
}
if (isset($_SESSION['isLoggedIn']) && $_SESSION['isLoggedIn'] == true) {
if (session_id() == '') {
session_start();
}
}
}
function login($user,$password) {
if (session_id() == "") {
session_start();
}
$_SESSION['isLoggedIn'] = false;
$mysqli = new mysqli(DB_HOST, DB_USERNAME, DB_PASSWORD, DB_DATABASE);
if ($mysqli->connect_errno) {
return false;
}
$user = $mysqli->real_escape_string($user);
$password = $mysqli->real_escape_string($password);
$query = "SELECT * from users WHERE email=$user";
if (!$result = $mysqli->query($query)) {
return false;
}
$row = $result->fetch_assoc();
$db_pass = $row['password'];
if (crypt($password,$db_pass) != $db_pass) {
return false;
}
$_SESSION['isLoggedIn'] = true;
if (session_id() == '') {
session_start();
}
return true;
}
}

Answer 1

Try changing your code to something like this
if (!isset($_SESSION['isloggedin'])) {
header("Location: login.php");
} else {
header("Location: home.php");
}

Answer 2

I was using AWS Elastic Beanstalk to run this web app. I didn't think this matter but apparently it did. It turns out that sessions don't work the same as they do on localhost since you are dividing your servers. I needed to enable sticky session within the load balancer.