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

Question

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>

This will display the source code instead of executing it:

<VirtualHost *>
    ServerName sourcecode.testserver.me
    DocumentRoot /var/www/example
    AddType text/plain php
</VirtualHost>

I used it once to enable other co-worker to have read access to the source code from the local network (just a quick and dirty alternative).

WARNING !:

As Dan pointed it out sometime ago, this method should never be used in production. Please follow the accepted answer as it blocks any attempt to execute or display php files.

If you want users to share php files (and let others to display the source code), there are better ways to do it, like git, wiki, etc.

This method should be avoided! (you have been warned. Left it here for educational purposes)

None of those answers are working for me (either generating a 500 error or doing nothing). That is probably due to the fact that I'm working on a hosted server where I can't have access to Apache configuration.

But this worked for me :

RewriteRule ^.*\.php$ - [F,L]

This line will generate a 403 Forbidden error for any URL that ends with .php and ends up in this subdirectory.

@Oussama lead me to the right direction here, thanks to him.

This might be overkill - but be careful doing anything which relies on the extension of PHP files being .php - what if someone comes along later and adds handlers for .php4 or even .html so they're handled by PHP. You might be better off serving files out of those directories from a different instance of Apache or something, which only serves static content.