I need help with PHP .htaccess rewrites

I have a url in the following syntax:
website.com/gallery/model/site/album/image

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
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.*)$ $1.php [NC,L]

RewriteEngine On
Options +FollowSymlinks
RewriteEngine on
RewriteRule ^gallery/([A-Za-z0-9_-]+)/([A-Za-z0-9_-]+)/([A-Za-z0-9_-]+)/([A-Za-z0-9_-]+)$ gallery.php?model=$1&site=$2&gallery=$3&image=$4 [NC,L]


The code above is from tutorials and me trying to implement them. I'm getting a 500 internal server error. I'm not sure how to put this rewrite together. Can I get some help? Thank you for those who took the time to read this.

 

Dear Glen,

I tried it, although am not good at REGEX but I have a small solution for you that may help.
Create index.php that will tackle all as per number of arguments.

Thus, your .htaccess

Options +FollowSymLinks
RewriteEngine On

    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^gallery/((?s).*)$ index.php?_url=/$1 [QSA,L]

Code (markup):

Your index.php

<?php

    $url = $_GET['_url'];
    $url = substr($url,1, strlen($url));

    list($data['model'],$data['site'],$data['album'],$data['image'])
            = preg_split('/\//', $url);

    print_r($data);

Code (markup):

then process the associative array called $data your way.

I hope it helps, let me know if you required more help.

stay well...