PHP / jQuery Ajax / Sessions Strange behaviour only on Chrome for Android - php

Question

I have been struggling with a couple of strange issues in my free time project I'm workig on. It's my first "big" PHP / JS project, and to be honest I'm using ajax for the first time so I might be just missing something.
Anyways, here how it is. I'm programming a very simple invoicing system using PHP and jQuery technologies with mPDF library to generate an PDF file from HTML/CSS. I'm using mainly Session variables inside the template that gets sent to mPDF to generate an PDF invoice.
Issue I'm experiencing is on Chrome for Android, tested on latest version on OnePlus One. The Session variables are not showing in the PDF itself. I think it worked like once or twice totally at random. My friend with Android device and Google Chrome also confirms same issue.
test.php:
<?php
session_start();
error_reporting(E_ALL);
if (!isset($_SESSION['GLO_IS_LOGGED_IN'])) {
header("Location: index.php");
exit;
}
include('libs/mPDF/mpdf.php');
ob_start();
include('protected/templates/template.php');
$data = ob_get_clean();
$mpdf = new mPDF();
$mpdf->WriteHTML($data);
$mpdf->Output('protected/invoices/Faktura ' . date('j-m-Y-H-i-s') . '.pdf');
$mpdf->Output('Faktura ' . date('j-m-Y-H-i-s') . '.pdf', 'D');
unset($_SESSION['VAR_DESCRIPTION_ARRAY']);
unset($_SESSION['VAR_AMOUNT_ARRAY']);
unset($_SESSION['VAR_PRICE_ARRAY']);
unset($_SESSION['VAR_TO_ADDRESS']);
unset($_SESSION['VAR_INVOICE_NUMBER']);
Here is generateInvoice.php file that you might have noticed in the invoice-script.js:
<?php
session_start();
error_reporting(E_ALL);
if (!isset($_SESSION['GLO_IS_LOGGED_IN'])) {
header("Location: index.php");
exit;
}
if (!empty($_POST['invoice-number'])) {
$_SESSION['VAR_INVOICE_NUMBER'] = trim($_POST['invoice-number']);
} else {
echo('Please add invoice number');
exit;
}
if (!empty($_POST['to-address'])) {
$_SESSION['VAR_TO_ADDRESS'] = ($_POST['to-address']);
} else {
echo('Internal Error');
exit;
}
$_SESSION['VAR_DESCRIPTION_ARRAY'] = $_POST['invoice-description'];
$_SESSION['VAR_AMOUNT_ARRAY'] = $_POST['invoice-amount'];
$_SESSION['VAR_PRICE_ARRAY'] = $_POST['invoice-price'];
I don't want to make this post very-long so I'll stop posting any code snippets here. Believe me that I have done everything I could to find out myself what's going on and it feels really bad that I cant figure it out myself and that I need to ask others for help. Anyways thanks for any feedback and help. Cheers!

Answer 1

'invoice-form' doesn't contain any fields - the input tags should be within the form

Answer 2

Ok people, I think I have found a solution for this.
Commenting away all of the unset methods at the end in test.php solved the Chrome for Android issue.
I don't understand why this was happening in the first place. Why were the session variables unset BEFORE the invoice was generated? They shouldn't be, right? Or I am really missing something? I know I shouldn't ask for clarification in my own answer but I think at this point I really need to.
Cheers and thanks to IanMcL for solving my Edge issue!