No, you didn't screw up anything. The locations that the LAMP in
that guide you posted uses will be the defaults for your centos'
RPMs locations. Just check the output of
for the location of your httpd.conf, look for your document root
and you're away laughing. The "other LLAMP" of yours is most likely
based on either a different distribution, or on someone elses idea
of what LAMP should be, and where it should live.