If you need to refer to your files using an extension different from their default one, you can add this rewrite rule to your .htaccess file:

Options +FollowSymlinks
RewriteEngine On
RewriteBase /
RewriteRule ^(.+)\.inx$ /$1.php [NC,L]

This way you will be able to open your .php files with .inx extension. For example, you will be able to refer to index.php as index.inx.