I use a package to generor the rss feed, but it show the message as below.

Warning: require_once(class.DomDocument.inc.php) [function.require-once]: failed to open stream: No such file or directory in…

The it will show me the fatal erro, It could not load file ‘class.DomDocument.inc.php’.
But the file does not include in the package.
And I could run these file in another server, so I guest the question made from a addon of php.

I modify the code to get the debug message:
class.RSSItemList.inc.php
class.ObjectList.inc.php
class.RSSItem.inc.php
class.RSS_V_200.inc.php
class.RSS_V_abstract.inc.php
class.DomDocument.inc.php <—-it does not include this file in the package.

I research the data in the google, someone says that , it need the libxml2 library.
But in the default ver. of apache in the linux platform, it include already.
And I research the others file about the XML and DOM.
Finaly, I got the answer, It need php-domxml addon.
Just install it through yum, and don’t forget restart apache.
Let the apache reload the php.ini , and it will load the addon for php.

command as below.
yum install php-domxml
service httpd restart