Works on any server with PHP installed

function get_user_id()
{
    $userid = NULL;
   
    // Get the logged in user's ID by cookie or session
    if (isset($_SESSION['userid']))
    {
        $userid = $_SESSION['userid'];
    }
 
    return $userid;
}

function get_avatar($image, $user_id)
{
    global $base_url;
   
    // Check if the file exists. If not, show the no avatar default image
    if (is_file($base_url . '/images/' . $image . '.gif'))
    {
        return $base_url . '../images/' . $image . '.gif';
    }
    else
    {
        return $base_url . AC_FOLDER_ADMIN . "/images/img-no-avatar.png";
    }
}

function get_link($link, $user_id)
{
    global $base_url;
   
	// Super easy - just return the user's profile URL
    return $base_url . '../users.php?id=' . $link;
}

function get_group_id($user_id)
{  
    global $db;
   
    $group_ids = array();
 
   
    // Get all the groups the user ID is in
    $result = $db->execute("
        SELECT group_id
        FROM " . TABLE_PREFIX . "user_group
        WHERE user_id = '" . $db->escape_string($user_id) . "'
    ");
 
    if ($result AND $db->count_select() > 0)
    {    
        while ($row = $db->fetch_array($result))
        {
            // Fill the group IDs into an array
            $group_ids[] = $row['group_id'];
        }
         
        return $group_ids;
    }
    else
    {
        return NULL;
    }
}