converting PHP to SSI
 

Ok here is the command for php I put in my main page: ?php include ("$as.php"); ?>

(with a < before the first ?)
with my navigator so I only have to edit the navigation section once. For the rest of the pages all I have to do is to add the contents. and to bring it together:
h**p://www.yoursite.com/index.php?as=downloads

and that includes my download and my nav page together.

My question is, how do I do this in SSI aka .shtml?