OpenCart Crashing / Displaying 500 Error when modifying footer.php

Whenever I make the slightest modification to the footer, I receive a 500 error. I have tried multiple browsers.
Closing the PHP tag makes the page display, but the footer clearly doesn't work.

I am installing OpenCart through cPanel's Softaculous Installer.
My hosting has PHP version 7.1 and all the required PHP extensions.

Help would be appreciated,
Many thanks.

Well, I think some more information is going to be required.

What files are you changing? what changes are you making.