Can I count sessions to determine number of people online?

Question

I am confused about something. When I try to search how to count online users in PHP, all answers related with MySQL and many different ways.

In my script, any user that submits the login form creates a $_SESSION['$nickname']

So I thought, can I count login sessions with count($_SESSION['$nickname']); and show it in my page?

Or is this totally a wrong logic?

Answer 1

Totally wrong logic. $_SESSION is a per-user thing. One user's session is not shared with any other user's session. Think about it - an online bank written in PHP, all sharing a single $_SESSION - everyone would see everyone's account details.

Assuming you're on the standard PHP file-based sessions, you can count the session files in whatever directory they're stored, e.g.

$users = count(glob(session_save_path() . '/*'));

Note that this just counts session files - it will undoubtedly contain stale/dead sessions that haven't been garbage collected yet. If you want an actual "really is online right now", you'd have to parse each session file and examin its contents.

Answer 2

At first, you have to define what "to be online" means. Should the user have clicked on a link within the last 5 minutes?

I assume that you already have a user table in your database. So the simplest way is to add a new column, e.g. lastAction TIMESTAMP.

And when the user clicks on a link on your page, your script should update this value.

And on your statistics page or whatever, you get the number of online users with that code:

SELECT COUNT(*) FROM users WHERE lastAction > (NOW() - 60*5)