When using MySQL to store session data, is it faster to use db queries instead of session?

I used a guide to redirect session requests to a DB call so I could maintain a session on front and backend PHP (this guide: from : https://culttt.com/2013/02/04/how-to-save-php-sessions-to-a-database/), but that leaves me with a question.

I can see that the session data is stored JSON in the db. Near as I can tell, that means every time I update $_SESSION data, the db is being called and sending the entire $_SESSION var back and forth.

Normally, I would store things in $_SESSION to ease calls to the db, but with DB sessions, that seems like it would make it far worse than normal. Or is using $_SESSION still pretty fast/memory only when reading and not writing?

For example, normally I’d get a user like this:

function get_user(userID) {
    if ($_SESSION['users'][userID]) return $_SESSION['users'][userID];
    $db = db_connect();
    $db->exec("SELECT * FROM users WHERE userID = ?",[userID]);
    $temp = $_SESSION['users'][userID] = $db->get_row();
    return $temp;
}

Point being, would it now be faster to just do the db call every time?

Answer

I’m accepting this comment (pasted as an answer) as the answer (credit to IncredibleHat):

---

If you only have a few thousand users, you won’t notice much of a difference in use. However if you are talking millions of users, then the constant get/store of the session data to a db table could start to show (by like an extra half second depending on your server). – IncredibleHat