LAMP: PHP not working (keeps downloading files.php)

Installed with a 1-click LAMP on my droplet (2 weeks ago). I now need to create a dynamic page using php, but if a create a file “test.php” with the following code:

<?php
echo "Hello!";
?>

instead of showing me an empty page which says “Hello!” it keeps downloading me test.php on my computer (when I connect to http://myip/test.php")! Please note: ‘test.php’ is in /var/www/html with index.html and many other .html files that work correctly. If I type php -v in the command-line it says that php 7.0.22-0ubuntu0.16.04.1 is installed. With LAMP i got installed Ubuntu 16.04 and Apache 2.4.18 (Ubuntu). When I type a2enmod php7.0 it says “Module php7.0 alredy enabled”.

I’m quite a newbie, so please help me… I have been searching for a solution for 2 days