<?php

$host = 'localhost';
$port = port;
$user = 'root';
$pass = 'pw';
$db = 'dbname';

mysql_connect("{$host}:{$port}", $user, $pass);
mysql_select_db($db);

print mysql_result(mysql_query("SELECT COUNT(*) FROM users users WHERE users.online = '1';"), 0);

?>