Before doing any work on your Ubuntu Server, it’s a good idea to update your software repositories using:
apt update
Once that has completed, you can install PHP and some of the packages that integrate it into your stack:
apt install php libapache2-mod-php php-mysql
You may also want to just tidy up what files Apache looks for when someone requests a directory:
vi /etc/apache2/mods-enabled/dir.conf
<IfModule mod_dir.c>
DirectoryIndex index.php index.html
</IfModule>As usual when making changes to apache, you’ll need to restart your service for changes to take affect:
systemctl restart apache2