$host = "myip";
$user = "root";
$pass = "";
$db = "mydatabase";

mysql_connect($host, $user, $pass);
mysql_select_db($db);
$on = mysql_fetch_row(mysql_query("SELECT COUNT(online) FROM characters WHERE online=1"));
echo "<br>Online: $on[0]<br><br>";

Warning: mysql_connect() [function.mysql-connect]: Host 'myip' is not allowed to connect to this MySQL server in * on line 46

Warning: mysql_fetch_row(): supplied argument is not a valid MySQL result resource in * on line 48

Online:

grant all privileges on mydatabase.*
   to youruser@'your_ip_address'
   identified by 'your_password';

flush privileges;