PHP opens 2nd session unwanted - php

Question

Requirement: use QRBOT-app to scan a barcode on a mobile and give the number scanned to the website.
Problem: I've a session open (1), from here I'm opening the app (see ScanBardcode.php), I scan and the app returns to the callback-URL including the required parameters. However I do expect it is re-using it's session, it creates a new one (2). Can someone help me? It does have both sessions active and both pages keep using it's own session. I can only test it on my cell phone, which I checked is using each time (the initiate-1 and the callback-2 the same browser)
What I tried already:
1. Pass the sessionID in the callback URL (QRBOT doesn't allow parameters)
2. Set Session.auto_start to 1
ScanBarcode.php
<?php
include_once('../../config.inc.php'); //contains DB connection details and other settings
include_once($fullurl . '../../admin/includes/sessie.inc.php'); //generates session
echo "SessionID=". session_id() . "!";
$_SESSION['BarCode'] = "VoorraadTellen";
echo "Wat gaan we doen? " . $_SESSION['BarCode'] . "</br></br>";
//URL to open qrbot.
echo "click"
?>
ScanBarcodeCallBack.php
<?php
$source = $_GET['x-source'];
$content = $_GET['content'];
$format = $_GET['format'];
include_once('../../config.inc.php');
include_once($fullurl . '../../admin/includes/sessie.inc.php');
echo "Wat gaan we doen? " . $_SESSION['BarCode'] . "</br></br>";
echo "SessionID=". session_id() . "!";
echo $source . $content . $format;
// HERE I WRITE TO THE DB.
?>
sessie.inc.php
<?php
$a = session_id();
if(empty($a))
{
session_start();
}
if(isset($_SESSION['sgebruiker']))
{
$now = time();
if($now - $_SESSION['stijd'] > $_SESSION['maxidle'])
{
$_SESSION = array();
session_destroy();
}
else
{
$_SESSION['stijd'] = $now;
}
}
elseif(isset($_COOKIE['login_cookie']))
{
//Check against db and set cookie.
}
?>
Adding screenshot when I add the sessionId in the URL as a parameter:
enter image description here
Update to ScanBarcode.php
`echo "click"

Answer 1

as far as i know you don't need the whole check with session_id(). PHP Documentation for session_start() says:
session_start() creates a session or resumes the current one based on a session identifier passed via a GET or POST request, or passed via a cookie.
this is also my experience. every time i used session_start() i just put it at the top of every file (or included it like you did)

Answer 2

When you pass the session ID in the URL, you need to use the parameter to set the session ID before calling session_start(). Change sessie.inc.php to:
<?php
if (isset($_GET['s'])) {
session_id($_GET['s']);
}
session_start();
if(isset($_SESSION['sgebruiker']))
{
$now = time();
if($now - $_SESSION['stijd'] > $_SESSION['maxidle'])
{
$_SESSION = array();
session_destroy();
}
else
{
$_SESSION['stijd'] = $now;
}
}
elseif(isset($_COOKIE['login_cookie']))
{
//Check against db and set cookie.
}
?>

Answer 3

Working with both #Tsai and #Barmar we found the solution.
We fixed it by:
- Encoding the URL by using urlencode-function
- Take the sessionID from URL and apply that using session_id-function before initiating the start_session (see also).
The cleaned up code below; hopefully someone would be able to use it also.
ScanBarcode.php
<?php
include_once('../../config.inc.php'); //contains DB connection details and other settings
include_once($fullurl . '../../admin/includes/sessie.inc.php'); //generates session
echo "SessionID=". session_id();
//URL to open qrbot.
$CallbackUrl = "http://ilonashairstyling.nl/2016UAT/module/Ilonas_admin/ScanBarcodeCallBack.php?s=" . htmlspecialchars(session_id());
echo "click"
?>
ScanBarcodeCallBack.php
<?php
$source = $_GET['x-source'];
$content = $_GET['content'];
$format = $_GET['format'];
include_once('../../config.inc.php');
ini_set("session.use_cookies",0);
ini_set("session.use_trans_sid",1);
session_id($_GET['s']);
//print_r($_SESSION); //You can test it with this code
//print(session_id()); //You can test it with this code
ini_set("session.use_cookies",1);
ini_set("session.use_trans_sid",0);
include_once($fullurl . '../../admin/includes/sessie.inc.php');
echo "Wat gaan we doen? " . $_SESSION['BarCode'] . "</br></br>";
echo "SessionID=". session_id() . "!";
echo $source . $content . $format;
// HERE I WRITE TO THE DB.
?>
sessie.inc.php is unchanged