Apache config on OS X Mavericks with Server
If you are running the "Server" product on your Mac with 10.9.x Mavericks, the apache httpd configs are not in the usual place (/etc/apache2).
You need to edit the files in
For example to enable PHP, edit httpserverapp.conf and uncomment php module load.
For each virtual host you create, there will be one (or more if you use SSL) config files in the "sites" subdirectory. Be careful to keep manual backups of these if you change them, because the Server app needs to be able to rewrite these, and sometimes will trample on your edits.