First, we need to give our current user (ubuntu) permission to edit files on the webserver, then we change to the web directory and move the old index.html file out of the way:
sudo chown ubuntu:ubuntu /var/www/html/ cd /var/www/html/ mv index.html old.html
Now, if you vist your IP address (the one we connect to via Putty/ssh) in your browser you should see a directory listing that contains one file (old.html)
We can create a new file called test.php containing some example PHP by typing this:
echo "<?php echo 'Hello, world'; ?>" > test.php
If you refresh your new website, now you should see two files: old.html and test.php
Clicking on test.php should show your newly created “Hello, world” program