System either does not have valid IP configuration or PHP is in a blocking state due to previous configuration
1. If you can ping yum.trixbox.org then skip to step 5
2. run the command: system-config-network to properly setup IP settings
3. using an editor like vi or nano, edit /etc/resolv.conf and make sure you have a valid DNS setting
4. run the command: /etc/init.d/network restart
5. run the command: service httpd restart