Accessing Variables in PHP Blocks

Hi All,

For each domain in the network of websites built using Domain Access, I would like to create customized messages. For instance, I would like to be able to create welcome and copyright blocks, whereby for each site, its respective domain and site name can be displayed in the block:

(c) Copyright 2009 echo <sitename>

What are the available variables and how can they be accessed? Are they in PHP?

I see that sometimes translation strings include template (I guess) variables such as %sitename.

How does this work best for Domain Access in general?

Much appreciated.

Thanks,
~DrupalFan