How secure is this?

I have setup a page that accesses mysql. The page has to included the account login name and password to access the mysql database. Example... <?php $user = "username"; //actual username goes here $pass = "password"; //actual password goes here $db = mysql_connect("localhost", $user, $pass)OR DIE("Unable to connect to database"); ?> If you get the idea. My concern is what if somebody can get to the source code. It could ruin me. I realise the php is a server side language, but is there any way that somebody could read this. If so how do i stop it? or is there another way to store my username & password that cannot be read. Please help Thanks Chris