to cover slightly more use cases, you could go for <?php include "header.php"; ?> like it's 2002, and then have that file just be plain html also. Of course if

to cover slightly more use cases, you could go for <?php include "header.php"; ?> like it's 2002, and then have that file just be plain html also. Of course if you're gonna pitch a solution that's impractical in most cases, you might as well go for the most extreme variant of that solution and not bother with that