[CentOS] Are PHP and MySQL running on my CentOS installation?

When I was installing CentOS, I noticed among the list of components
that PHP and MySQL were available. I made sure they were selected
because I develop a lot of web sites in PHP/MySQL, but I always do my
testing on the server side. I thought it would be kind of cool if I
could do the testing and development on my home machine.

Which is a long way of saying that I think I have PHP/MySQL on my
machine, but have no idea what the heck to do with them. I mean, I can
script PHP and write queries for MySQL, but don't know anything about
their set up and installation.

I wrote a small test HTML page with basic head and body information, and
simply this PHP in the body:
<?php
echo 'hello world':
?>
And then opened it in FireFox. As expected, it didn't display anything.

So I went to my trusty friend, Google, and asked about it. But it's one
of those cases where people seem to assume that it's already installed,
and if it's installed, it's already working. The PHP site itself says
"We do not distribute UNIX/Linux binaries. Most Linux distributions come
with PHP these days" and then not much else about running it.

Am I going to find myself in a whole new world of confusing settings and
configurations if I try to get PHP working on my home machine? 

Dave