Pedantic troubleshooting guide

Can anyone point me to an extremely pedantic troubleshooting guide ?? This is the first time I’ve messed with PHP for yonks after tearing my hair out in utter frustration and swearing many years ago that I’d never touch it again. As far as I can tell, the apache module is loading and php ‘appears’ to be working if the test described at https://www.digitalocean.com/community/tutorials/how-to-install-an-apache-mysql-and-php-famp-stack-on-freebsd-10-1 is any indication. On the other hand, apache seems to have taken a dislike to PHP and only shows the default ‘It Works’ page. I figure there are probably a few issues I need to resolve, hence the request for an elementary level testing protocol to get to the bottom of the problem(s). For what its worth, I don’t generally have any issues with apache websites, but then I’ve managed to avoid PHP almost since the dawn of time.