So I was developing a small php app which used DOM manipulation classes on my local Ubuntu machine. Everything went fine. Then I uploaded my app to the server which ran Fedora. My app would not work. The DOM classes were not recognized. It turned out that out of the box, php installation in Fedora did not include php-xml package which was needed for DOM manipulation. So, I had to install it.

su
yum install php-xml
yum install php-xmlrpc