Farkli hostta ise 2. mySQL DB, remote connection iznine sahip olmalisin, sonrasinda islem yapmak icin ise;

<?php
$connection = mysql_connect('locahost', 'user', 'password');
mysql_select_db('database', $connection);

$connection2 = mysql_connect('locahost', 'user2', 'password2');
mysql_select_db('database2', $connection2);

# Sorgulariniz 1. DB icin
mysql_query("SELECT * FROM tablo", $connection);

# Sorgulariniz 2. DB icin
mysql_query("SELECT * FROM tablo", $connection2);
?>