Assuming the primary key for db1 is 'ID':
$db->beginTransaction();
$Process = $db->prepare("UPDATE db1 SET num = ?, usd = ?, btc = ?, date = ? WHERE ID = ?");
$Process->execute(array($_GET['op'], $_POST['usd'], $_POST['btc'], date('Y-m-d H:i:s'), $r['id']));
echo 'Processed.
'
;
$db->commit();
?>