<IfModule mod_headers.c>
Header set Strict-Transport-Security max-age=16070400;
</IfModule>

RewriteEngine On

# Don't rewrite if the URL already ends in .php
RewriteCond %{REQUEST_URI} !\.php$ [NC]

# Don't rewrite if the request is for a real file or directory
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# Rewrite /page to /page.php
RewriteRule ^([^/]+)$ $1.php [NC,L]