You should read available changes informations: All Changelogs

This new version is bundled with the XML_Util extension, so the php-pear-XML-Util is obsoleted.

Al always, just yum it:

yum --enablerepo=remi update php-pear

You can also download the RPM from the repository

As Fedora 11 is freezed, we have to wait a little before it will be available in the official repository (probably for Fedora 12)