Disable PHP in directory (including all sub-directories) with .htaccess

I'm making a website which allows people to upload files, html pages, etc... Now I'm having a problem. I have a directory structure like this:

-/USERS
    -/DEMO1
    -/DEMO2
    -/DEMO3
    -/etc... (every user has his own direcory here)
-index.php
-control_panel.php
-.htaccess

Now I want to disable PHP, but enable Server-side includes in the direcories and subdirectories inside /USERS

Can this be done (and how :) )? Thanks in advance.

BTW, I use WAMP server

Try to disable the engine option in your .htaccess file:

php_flag engine off

To disable all access to sub dirs (safest) use:

<Directory full-path-to/USERS>
     Order Deny,Allow
     Deny from All
 </Directory>

If you want to block only PHP files from being served directly, then do:

1 - Make sure you know what file extensions the server recognizes as PHP (and dont' allow people to override in htaccess). One of my servers is set to:

# Example of existing recognized extenstions:
AddType application/x-httpd-php .php .phtml .php3

2 - Based on the extensions add a Regular Expression to FilesMatch (or LocationMatch)

 <Directory full-path-to/USERS>
     <FilesMatch "(?i)\.(php|php3?|phtml)$">
            Order Deny,Allow
            Deny from All
    </FilesMatch>
 </Directory>

Or use Location to match php files (I prefer the above files approach)

<LocationMatch "/USERS/.*(?i)\.(php3?|phtml)$">
     Order Deny,Allow
     Deny from All
</LocationMatch>

If you're using mod_php, you could put (either in a .htaccess in /USERS or in your httpd.conf for the USERS directory)

RemoveHandler .php

or

RemoveType .php

(depending on whether PHP is enabled using AddHandler or AddType)

PHP files run from another directory will be still able to include files in /USERS (assuming that there is no open_basedir restriction), because this does not go through Apache. If a php file is accessed using apache it will be serverd as plain text.

Edit

Lance Rushing's solution of just denying access to the files is probably better

<Directory /your/directorypath/>
     php_admin_value engine Off
</Directory>