php...
<?php
$con = mysql_connect("host", "mysql_user", "mysql_password");
mysql_select_db("database", $con);
$metrima = mysql_query("SELECT * FROM characters WHERE online = '1'", $con); //den eimai sigouros gia tin syntaksi tis entolis
$num_rows = mysql_num_rows($metrima);
echo "$num_rows Players online\n";
?>