What is the purpose of the user-online script in PHP and what is the main issue with the current implementation?

The current implementation of the user-online script in PHP is inefficient because it queries the database on every page load to update the user's last online time. This can lead to unnecessary database calls and increased server load. To solve this issue, we can update the user's last online time only when they log in or log out.

// Update user's last online time only when they log in or log out
function updateLastOnlineTime($userId) {
    // Update last online time in the database for the user with $userId
    // This function should be called when the user logs in or logs out
}

// Example usage:
// Call updateLastOnlineTime function when user logs in or logs out
updateLastOnlineTime($userId);