Grav not running installed PHP 7

I have downloaded from the grav web site and unzipped the archive into the default /var/www/htdocs folder. As far as I can see all files are present as indicated in the docs.

All the system requirements for grav have been met including the use of PHP 7. It is located in /usr/lib/php. However, when attempting to install grav any php page (like index.php) displays the PHP text in the browser and does not execute PHP.

I can run the scripts supplied. In fact i tried to run the bin/gpm install admin but got an error
Class 'ZipArchive' not found when attempting to install the Form package.

I know I am missing something somewhere.

Well, it sounds like you don't have PHP running properly with PHP. If you create a simple testfile.php with:

<?php echo "hello world"

Does that work? I think probably not.

Hi. I have 2 weeks use Grav with php7, no problem. Used 2 sites, one working, the other in development.