How to keep track of multiple request data from the same user in PHP sessions?

Question

So the question is a little complicated, let me explain. My page code is running like this:

1. User enters query in the search field and clicks submit.

   1.1 jQuery loads a new body to display progress data.

   1.2 jQuery calls process.php via AJAX and supplies query as the argument.

   1.3 jQuery starts setInterval periodic update to grab progress data, stored inside $_SESSION['prog'], and displays it.

2. When process.php finishes, jQuery stops periodic update, displays final information and calls AJAX to clear the $_SESSION['prog'] variable.

At the moment progress data is stored inside one variable, which is fine as far as different users are concerned (because of the different sessions), but if the same user were to make multiple requests at the same time, the $_SESSION['prog'] variable would be cross-overwritten.

So far I have thought of two possiblities to distinguish data for each request from the same user (same session)

1. Have jQuery generate some random string and send it together with query (and hope to avoid colission, although that would be unlikely)

2. Make 2 AJAX calls, first one requesting new_request_id, the second one sending query and new_request_id as parameters.

3. Have AJAX return something from PHP before is finishes(completes).

I need to connect each browser window (each request) with each running process, so I cannot send back new request ID after the request has been submitted, because I wont know which data to pick up with jQuery in the browser window. Btw, I will change $_SESSION['prog'] to $_SESSION[request_id] -> request_id is what I'm looking for.

It (request_id) could be last_insert_id(), because im creating new DB entries for each valid query, but I don't know how to get it back to each different user window.

I need advice here. Only just begun to code in PHP, AJAX and jQuery, don't really know much about sessions. How should I solve this problem?

Sorry for the lack of code, I will paste is at request.

Answer 1

You could add a unique ID to each request in addition to the session ID. eg. uniqid() in javascript/jquery?

Answer 2

You need to differentiate them somehow. For example use a unique ID autonumber field. MySQL has last_insert_id() which is very useful and handles concurrent requests correctly.

Answer 3

Avoid using Session variables in Ajax requests. Send them with GET (or POST) instead. Even if calling Session_start(); in the Ajax request and getting $_SESSION['prog'] from there, results can be unexpected.