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

RewriteCond and RewriteRule in .htaccess

I have a client folder located at http://www.example.com/client However, I've now installed SSL on the server, and want to add a permanent redirect using HTACCESS so that whenever /client is accessed, that it redirects to: https://www.example.com/client

Anybody know how to do that?

I've redirected my domains in the past like this:

RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]
RewriteCond %{HTTP_HOST} ^www.example\.com$ [NC]
RewriteRule ^(.*)$ http://www.example.com/$1 [L,R=301]

This should not affect the solution, but the site must still redirect to www.example.com FIRST, and then to https://www.example.com/client if for example, http://www.example.co.za/client is entered.