How to install PHP and activate SSL

I'm trying to move a PHP application to our web hosting account with OVH Cloud. I've uploaded the files and modified the configuration file to point it at the database. It runs as a subdomain of our main domain.

When I try to load the site using the Windows Hosts file to point the domain at the OVH space, the first thing I see is a warning that the connection isn't secure and I can then proceed via http.

Once clicked that then shows the PHP code of the files in the browser, it doesn't execute them. Because of this I don't want to provide a link to this.

I thought this might be because something called Ioncube needs to be installed, but to do that, I need PHP files to execute. At the moment when called I just see the PHP code in the web browser.

The settings for the virtual hosting plan show Global PHP Version 8.3 with a green tick next to it. The "Multisite" page shows the subdomain (e.g. support.mydomain.com) pointing at the right folder in the webspace and if I put up an index.html file there, it will render.

I've tried selecting different PHP versions, but PHP is definitely not executing regardless.

The settings for that subdomain show SSL as enabled.

How do I enable SSL and PHP? Thank you.