Even better, create a file that only root can read, /path/to/secret-stuff.

SetEnv DB_HOST "example.org"
SetEnv DB_USER "myuser"
SetEnv DB_PASS "mypass" 
Include this in httpd.conf.

Include "/path/to/secret-stuff" 
db.inc is better now.

<?php

$db = mysql_connect($_SERVER['DB_HOST'], $_SERVER['DB_USER'], $_SERVER['DB_PASS']);

?>