PHP files prompts downloaded instead of executed in FCGId URL

In "/etc/apache2/mods-enabled/php.conf" (replace php with your filename, depending on the php version you're using - in my case it was php7.2.conf) comment out the following two lines:

SetHandler application/x-httpd-php

SetHandler application/x-httpd-php-source

Restart the apache server via the following command:

sudo service apache2 restart

Now set your webstite to FCGId (Virtualmin -> Server Configuration -> Website options -> PHP script execution mode ) and it should work properly.