PHP - Cannot change session variable in an "if" statement - php

Question

Trying to make a page redirect if not logged in. I'll try to show what I mean.
In the index.php:
<?php
// initialization of login system and generation code
$oSimpleLoginSystem = new SimpleLoginSystem();
echo $oSimpleLoginSystem->getLoginBox();
session_start();
$_SESSION["loggedin"] = False;
// class SimpleLoginSystem
class SimpleLoginSystem {
// variables
var $aExistedMembers; // Existed members array
// constructor
function SimpleLoginSystem() {
$this->aExistedMembers = array(
'test' => MD5('test'), //Sample: MD5('qwerty')
);
}
function getLoginBox() {
ob_start();
require_once('login_form.html');
$sLoginForm = ob_get_clean();
$sLogoutForm = 'logout';
if ((int)$_REQUEST['logout'] == 1) {
if (isset($_COOKIE['member_name']) && isset($_COOKIE['member_pass']))
$this->simple_logout();
}
if ($_REQUEST['username'] && $_REQUEST['password']) {
if ($this->check_login($_REQUEST['username'], MD5($_REQUEST['password'])))
{
$_SESSION["loggedin"] = True;
$this->simple_login($_REQUEST['username'], $_REQUEST['password']);
header( 'Location: /site.html' );
}
else {
return 'Username or Password is incorrect' . $sLoginForm;
}
} else {
if ($_COOKIE['member_name'] && $_COOKIE['member_pass']) {
if ($this->check_login($_COOKIE['member_name'], $_COOKIE['member_pass'])) {
header( 'Location: /site.html' );
}
}
return $sLoginForm;
}
}
In the site.php:
<?php
session_start();
if ($_SESSION["loggedin"] == 0)
{
header( 'Location: http://test-weeabear.c9users.io/' );
}
else
{
return "It worked!"
}
?>
Why is it when I open site.html, it redirects me back to index.html, even after logging in?
NOTE: Some things I changed, like links and names of files. For privacy.

Answer 1

You need session_start() at the start of your site.php

Answer 2

change the file extension from .html to .php

Answer 3

You are calling getLoginBox and then changing the loggedin back to false. You need to include an exit after the header redirect.
Like this:
header( 'Location: /site.php' );//changed to file extension as .php
exit;