Remembering PHP Session Private Browsing

Question

I'm developing an analytics script that people will be able to add to their page in order to track visitor data. One of the issues I've come across is devising a way to track individual's sessions when they're viewing someone's page from a private browser (I.e. Incognito).

This is the script I'm using to see if someone to observe if someone has been active for more than 30 minutes, if they have, a new session will be created, if not, then they will resume their previous session.

        session_start();
        $max_time = 1800;
        $current  = time();
        if (!isset ($_SESSION['Stationary'])){
            $_SESSION['Stationary'] = time();
            $session = $_SESSION['Stationary'];
        }
        if (!isset ($_SESSION['Inactive'])) { 
            $_SESSION['Inactive'] = time();
        } else {
            $session_life = $current - $_SESSION['Inactive'] ;
            if ($session_life > $max_time ) {
                session_destroy();
                session_start();
                $_SESSION['Inactive'] = time();
                $_SESSION['Stationary'] = time();
                $session = $_SESSION['Stationary'];
            } else {
                $_SESSION['Inactive'] = time();
                $session = $_SESSION['Stationary'];
            }
        }

This script works flawlessly when a user views my page from a regular browser (IE. Chrome Incognito), however when they view it on something like an iPhone, in Private Browsing, every time they access a new page, a new session is rendered -- a problem that I do not have when viewed otherwise.

So my question then is, I'm aware that viewing pages in a Private Browser is achieved through temporary cacheing which is cleared once the browser is closed, however why is it that even when the browser is not closed, opening a link destroys their previous session even when the link leads to another page, with the same script on the page?

Is there a workaround to this?

EDIT: I should note that this script is being placed in a php file with the header application/json to be used as a JavaScript file as well.

Answer 1

If we firstly look at php session documentation

A visitor accessing your web site is assigned a unique id, the so-called session id. This is either stored in a cookie on the user side or is propagated in the URL.

Secondly, what mozilla support says about private browsing (pretty much the same for other browsers)

What does Private Browsing not save? Cookies!

So the answer is clear now: the browser is not saving any of cookies that are used by php in order to retrieve the respective session.

Is there a workaround to this?

Yes. The $_SERVER variable holds data that can be considered as unique. For example, try using REMOTE_ADDR combined with parsed data from HTTP_USER_AGENT and CRUD it (database, probably).

Some extra info

• How to get the client IP address in PHP?
• Get users OS and version number