PHP - Session per Tab

PHP stores session IDs in cookies and cookies are per client (browser), not tab. So there is no simple and easy way to do this. There are ways of doing this by creating your own session handlers, but they are more hacks than solutions and as such come with their own risks and complexity. For whatever reason you may need this, I am quite sure that there is a better architectural solution than session splitting.

I've been scouring the web for answers to this problem and have not yet found a satisfying solution. I finally pulled together something in JavaScript that sort of works.

//generate a random ID, doesn't really matter how    
if(!sessionStorage.tab) {
    var max = 99999999;
    var min = 10000000;
    sessionStorage.tab = Math.floor(Math.random() * (max - min + 1) + min);
}

//set tab_id cookie before leaving page
window.addEventListener('beforeunload', function() {
    document.cookie = 'tab_id=' + sessionStorage.tab;
});

HTML5 sessionStorage is not shared between tabs, so we can store a unique tab ID there. Listening for the beforeunload event on the window tells us that we're leaving (and loading some other page). By setting a cookie before we leave, we include our value in the new request without any extra URL manipulation. To distinguish between tabs you just have to check $_COOKIE['tab_id'] on the server and store sessions values appropriately.

Do note that Firefox behaves strangely, in that triggering window.open() will create a window that shares sessionStorage with its parent, giving you two tabs with the same ID. Manually opening a blank tab and then navigating to the target URL will give you separate storage. Chrome works for me in all of my tests so far.

I realize this is probably not the right answer, or even a "good" answer, but it is an answer.