[eluser]Joshua Logsdon[/eluser]
Just another note on top of GnomBrother, if you want to stick to your pure php way... just make a separate constants file (similar to /application/config/constants.php) outside of www, include it at the top of your /applications/config/database.php file and then assign as necessary.
CI is pure php
it just may feel a little odd to go outside of the "framework conventions mindset" to do what you need. Compared to hacking up or overriding core stuff though, this is pretty minor.
