2
You may want to check out this link:
Xoops HTML Pages. I know that you are not wanting to insert html into a XOOPS page, but putting a php script into a XOOPS page works on the same basic idea. All you really need to do is create a file like this:
include("path/to/mainfile.php");
//This line includes the XOOPS header at the top
//which includes the navigation bars, etc.
include(XOOPS_ROOT_PATH."/header.php");
//The content of your original html file goes here!!
//You can actually enter your php text in here,
//or you could include your file directly like this...
//include("yourfile.php");
//This includes the XOOPS footer at the bottom of the page
include(XOOPS_ROOT_PATH."/footer.php");
?>