It depends on how funky you want to get with your config ... if it's simple enough, PHP code and Perl code can look identical:
$domainname = 'example.com';
$page_background = '#ccffff';
If you start in on arrays, the syntax begins to differ of course, and actual code probably wouldn't carry across, only ... no, I can't think of a way to comment the code so that PHP reads PHP and a big comment and Perl reads a big comment and Perl.
You can have comments, of course: PHP and Perl both use # to start a one-line comment.