<Directory /var/www/>
    <IfModule mod_rewrite.c>
        RewriteEngine On

        RewriteCond /%{REQUEST_FILENAME}.php -f
        RewriteRule ^([a-zA-Z0-9_-s]+)/$ /$1.php

        RewriteCond /%{REQUEST_FILENAME}.html -f
        RewriteRule ^([a-zA-Z0-9_-s]+)/$ /$1.html
    </IfModule>

    <IfModule mod_expires.c>
        ...
    </IfModule>

    <IfModule mod_headers.c>
        ...
    </IfModule>
</Directory>