What strategies can be used in PHP to determine the online status of users and accurately track their activity for access control purposes?

To determine the online status of users and accurately track their activity for access control purposes, we can use a combination of session management and database tracking. By storing user login/logout timestamps in a database and updating session variables accordingly, we can keep track of when users are online and offline. Additionally, we can use session variables to store user activity information and implement access control based on this data.

// Check if user is online based on session variables
session_start();
if(isset($_SESSION['user_id'])){
    // Update user's last activity timestamp in the database
    $user_id = $_SESSION['user_id'];
    $last_activity = time();
    // Update user's last activity timestamp in the database
    // Implement access control based on user activity
}