php - GET and POST request not working for a ip-address (Internal server error) -

working on application have migrate server i.e. amazon.now created ec2 instance,configured , installed application.all fine ajax requests giving me internal server error 501 message.
i have same application running on different domain(i migrating amazon) , works fine.on amazon have ip-address @ application runs , not have domain name.(i.e x.x.x.x/home.php). cross checked paths trying both absolute , relative urls,but still same error,even though file present.
also,i tried changing permissions 644 755,but no result.
inputs on if happening because i don't have domain name yet ip(it works fine on old server godaddy 1 , has domain name pointed it)?

php 5 should come dom enabled default. can check inspecting php info output.

dom  dom/xml enabled dom/xml api version 20031129 libxml version  2.7.8 html support    enabled xpath support   enabled xpointer support    enabled schema support  enabled relaxng support enabled 

if using php 5 , reason dom not available. check package in repositories called php5-xml