How can a PHP forum determine which users are currently online and which are not?

To determine which users are currently online in a PHP forum, you can use a combination of session tracking and timestamp checking. When a user logs in, set a session variable with their user ID and a timestamp indicating their last activity. Then, periodically check the timestamps of active sessions to determine which users are currently online. 

// Check if user is currently online
session_start();

// Set user's last activity timestamp
$_SESSION['last_activity'] = time();

// Check active sessions to determine online users
$timeout = 300; // 5 minutes timeout
$online_users = array();

foreach ($_SESSION as $key => $value) {
    if ($key !== 'last_activity' && (time() - $value) < $timeout) {
        $online_users[] = $key;
    }
}

// Display online users
echo "Online users: " . implode(', ', $online_users);

Keywords

PHP forum online users session management tracking

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