config items versus constants, seeking clarification.

[eluser]skunkbad[/eluser]
[quote author="nuwanda" date="1291120844"][quote author="skunkbad" date="1291117792"]I define constants in hooks so that I can use them before config items are set. I use config items when they are specifically related to some library or code, to help keep things organized.[/quote]

Just out of interest, what exactly are you using your hooks for?[/quote]

I have a hook that sets up $_SESSION, and another for a custom error handler. I also have one that sets the X-Powered-By header.