Allow PHP to access files but not website visitors

Add the following to an .htaccess file, and all .php files under the .htaccess file will not be available via the web:
<FilesMatch "\.php$">
Order deny,allow
Deny from all
</FilesMatch>

The files will be available through PHP though. As PHP is not requesting the files through Apache webserver, rather is it requesting include files via the file system.