Disabling php execution for a certain virtual domain is incredibly simple:
All you need to do is add:
php_value engine off
That could be anywhere in your VirtualHost directives.
Another possible approach is through enabling .htaccess for a domain, e.g.:
AllowOverride All to your domain of choice.
After which you had to put:
php_flag engine off to htaccess file
Now there you go! php scripts won’t execute anymore.