I need help with PHP .htaccess rewrites

I have a url in the following syntax:

The main file handling the variables is gallery.php. The categories following gallery in the url are to be the variables: $model $site $album $image in php. I want the php extension removed, and the 4 variables routed to the gallery page. This has been giving me a lot of trouble. What I have so far in my .htaccess file is:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f...

I need help with PHP .htaccess rewrites

Poster :
Glen Huff