TaneMahuta TaneMahuta - 1 month ago 3x
PHP Question

PHP: How to check if user is already logged in and otherwise redirect to login page

I am new to PHP and am struggling with the following:

I have a page where I want to check if someone is a registered user before letting them see the content of the site.
So my thought was that in my header file (which is referenced on all single pages via

) I can check on that and redirect them to a login page (
) if they have not logged yet.

So here is everything that I have in my header:

<!DOCTYPE html>
define("someUnguessableVariable", "anotherUnguessableVariable");
if(!(isset($_SESSION['login']) && $_SESSION['login'] != '')){
header ("Location: login.php");

include "system/config.php";

$pageURL = basename($_SERVER["REQUEST_URI"]);
$pageName = pathinfo(parse_url($pageURL, PHP_URL_PATH), PATHINFO_FILENAME);

$selectedLang = $_GET["lang"];
$selectedLang = "de";
$langURL = "?lang=" . $selectedLang;

$conn = new mysqli($dbServer, $dbUser, $dbPass, $dbName);
die("Connection failed: " . $conn->connect_error);
// fetch main translations
$location = "%main%";
$stmt = $conn->prepare("SELECT tID, " . $selectedLang . " FROM TranslationsMain WHERE location LIKE ? ORDER BY tID");
$stmt->bind_param("s", $location);
$result = $stmt->get_result();
while($arrTranslations = $result->fetch_assoc()){
$trans[] = array("ID" => $arrTranslations["tID"], "trans" => $arrTranslations[$selectedLang]);

// get main translations by ID
function fetchTransMain($trans, $itemID){
foreach($trans as $key => $val){
if($val["ID"] == $itemID){
return $val["trans"];

<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="author" content="Some author" />
<meta name="description" content="Created: 2015-06" />

<base href="http://www.myurl.de" target="_self" />

<title>Some title</title>

<!-- CSS -->
<link rel="stylesheet" type="text/css" href="includes/styles.css" />
<!-- CSS - Font Awesome -->
<link rel="stylesheet" type="text/css" href="http://maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css" />

<!-- include favicon -->
<link rel="shortcut icon" href="images/favicon/favicon.ico" type="image/x-icon" />
<link rel="icon" href="images/favicon/favicon.png" type="image/png" />
<link rel="icon" sizes="32x32" href="images/favicon/favicon-32.png" type="image/png" />
<link rel="icon" sizes="64x64" href="images/favicon/favicon-64.png" type="image/png" />
<link rel="icon" sizes="96x96" href="images/favicon/favicon-96.png" type="image/png" />
<link rel="icon" sizes="196x196" href="images/favicon/favicon-196.png" type="image/png" />
<link rel="apple-touch-icon" sizes="152x152" href="images/favicon/apple-touch-icon.png" />
<link rel="apple-touch-icon" sizes="60x60" href="images/favicon/apple-touch-icon-60x60.png" />
<link rel="apple-touch-icon" sizes="76x76" href="images/favicon/apple-touch-icon-76x76.png" />
<link rel="apple-touch-icon" sizes="114x114" href="images/favicon/apple-touch-icon-114x114.png" />
<link rel="apple-touch-icon" sizes="120x120" href="images/favicon/apple-touch-icon-120x120.png" />
<link rel="apple-touch-icon" sizes="144x144" href="images/favicon/apple-touch-icon-144x144.png" />
<meta name="msapplication-TileImage" content="favicon-144.png" />
<meta name="msapplication-TileColor" content="#ffffff" />

var baseURL = '<?php echo $baseURL; ?>';
var pageURL = '<?php echo $pageURL; ?>';
var pageName = '<?php echo $pageName; ?>';
var selectedLang = '<?php echo $selectedLang; ?>';

Now this is not working and I think I am probably missing a couple of things but I couldn't find a good tutorial or guideline on that.
Also, I am not sure if there is anything else I need to do in order to start and set up the session.

Can someone help me with this ?


This is only about checking if a user is already logged in since all the actual user registration and verification is done on the separate login page and for this I already have the code working.

Enabling error messages returns the following errors:

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /homepages/21/d580042014/htdocs/index.php:2) in /homepages/21/d580042014/htdocs/includes/header.php on line 9

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /homepages/21/d580042014/htdocs/index.php:2) in /homepages/21/d580042014/htdocs/includes/header.php on line 9
array(0) { }
Warning: Cannot modify header information - headers already sent by (output started at /homepages/21/d580042014/htdocs/index.php:2) in /homepages/21/d580042014/htdocs/includes/header.php on line 12

Notice: Undefined index: lang in /homepages/21/d580042014/htdocs/includes/header.php on line 18


As per the comments I now posted everything that's currently in the header.

Many thanks in advance.


Update: The question has been resolved in chat.

As per your edit, change this block:

<!DOCTYPE html>
            define("someUnguessableVariable", "anotherUnguessableVariable");
            if(!(isset($_SESSION['login']) && $_SESSION['login'] != '')){
                header ("Location: login.php");



<!DOCTYPE html>
            define("someUnguessableVariable", "anotherUnguessableVariable");

            if(!isset($_SESSION['login']) && $_SESSION['login'] != ''){
                header ("Location: login.php");
                exit; // stop further executing, very important
  • Follow the same structure for starting the session in all your files using sessions.
  • Make sure that your file does not have a byte order mark (BOM).
  • No space before <?php etc. this has already been established in comments.

Using a code editor such as Notepad++ https://notepad-plus-plus.org/ and to save it as UTF-8 without BOM which will ensure there is no byte order mark.

Also, using the new method for your sessions array check.

if(!isset($_SESSION['login']) && $_SESSION['login'] != ''){

Also check to see that none of your included/required files have the same issues, including login.php.


Inside Notepad++'s dropdown menu, you will see

  • Encoding. It will show you what the present file's encoding is set to.

If it does show a byte order mark, follow these steps:

  1. Click on "Encoding".
  2. Convert to UTF-8 without BOM
  3. Save the file.

    • Do this for all your files.



You should change $stmt->execute(); to

    trigger_error("there was an error....".$conn->error, E_USER_WARNING);
  • It's better to catch possible errors in your query.