Looking for a universal header navigation solution.

Sorry if the title is a bit unclear, but I'm building a site that has a navigation header in the top and I'm looking for the best solution to have it appear on every single page, including subdomains.

The idea is that I will use the navigation header you see here http://zest.explosiveapps.com/navigation.php (by the way I know the twitter feed isn't working at the moment)

Right now there is a website on http://www.explosiveapps.com/ that will be moved to it's own subdomain, sleepstream.explosiveapps.com and so will other apps and the blog. The company pages like contact, about and apps will be explosiveapps.com/contact.php, about.php and apps.php

Ideally the header navigation would not reload, but this is not a must. And it's always there even if I go directly to a subdomain. The thing is that it would be nice not having to add the header to every single page that a subdomain would have, for example to all the sleepstream pages, a bit cleaner in other words.

Hope you understand what I'm trying to say here. Would it be better if I posted this in PHP? Thanks for looking at my mess and have a nice day.

Cheers
M.

I guess you could use a frame, but that is unfriendly for SEO. So you'll probably just have to use a PHP include statement, unless you wanted to use a server-side include. If your pages are being parsed by PHP anyway, you may as well use PHP includes.