WordPress MU

Ok, done some research searching for this, but no luck. I've setup wordpress MU to be a massive CMS for a site. The main blog functions as the main site and all sub-blog are mini sites. I have a couple themes developed and customized for each sub-blog site. My question is how I can share say a footer across all themes so if I make a change its site-wide and I don't have to edit footer.php in every theme I create.

I'm using a main images folder outside the themes directory and then using absolute paths to the source, but I'm running into issues calling PHP files that I want to share with each theme. Any ideas?

You can create a footer.php file in one theme, then use the PHP include in the footer.php of each theme you make thereafter. That way, the first footer.php file acts as the "master". I do that on a few sites that need the same footer but different templates.

"My question is how I can share say a footer across all themes so if I make a change its site-wide and I don't have to edit footer.php in every theme I create."

Hook into wp_footer in a little plugin. Then, just change what you want in the plugin and all footers get updated.

http://wpmututorials.com/plugins/how-to-hook-into-the-footer/