What are some best practices for tracking user activity and online status in a PHP-based website?

Tracking user activity and online status in a PHP-based website can be achieved by using sessions or database entries to store user activity timestamps. By updating these timestamps regularly, you can track when a user was last active and determine their online status. Additionally, you can use AJAX requests to periodically update the user's activity status without requiring a page reload.

// Update user activity timestamp in session
session_start();
$_SESSION['last_activity'] = time();

// Check if user is online based on last activity timestamp
function isUserOnline($timeout = 300) {
    if(isset($_SESSION['last_activity']) && (time() - $_SESSION['last_activity'] <= $timeout)) {
        return true;
    }
    return false;
}

// Example usage
if(isUserOnline()) {
    echo "User is online";
} else {
    echo "User is offline";
}