A php script can do whatever you instruct it to, for any page on which you run it 
What you really want to do is to include a piece of HTML. You can do this using the php include() function. If you have been following Dan's tutorials at the GN, this practice is covered pretty well.
Basic concept: create one file with your navigation. use the include() function to include that file on whatever page you want it displayed.
A typical page template for me will be setup like this -
file 1: header.php
- this file includes the start of the HTML document, from the DOCTYPE, head element, open of the body tag, and whatever navigation will start the page (which doesn't just have to be at the top...a side navigation will fit this way just as easy), usually ending the with opening of a <div id="content">
file 2: footer.php
- this file closes the open 'content' div, the body tag, and the html tag. It may or may not also contain a <div id="footer"> with whatever relevant content is needed there.
actual page files
- these files are the actual content of the site. each one will start and end with a bit of php which will include the header and the footer, with all content in between.
There is no limit to the number of pages, and no limit to what you can include in this manner.
(Edited by DL-44 on 11-10-2006 04:24)