If you are running your own webserver, then look into installing "suPHP" instead of the normal PHP modules. For RedHat compatible systems, it's usually as easy as "yum install suphp".
suPHP makes the PHP process run as the user who owns the PHP files, meaning that the script has the necessary permissions to update itself directly. No more FTP info required.
suPHP is pretty much the standard for shared hosting setups, as it ensures that somebody hacking into one website won't have sufficient permissions to hack into the other sites on that server through the same means (assuming everything is chmodded correctly, of course).