I already wrote about upgrading via Jason Litka repo on this PAGE but in case you have problems with this repo, you can add Remi Collet repo.
First, import Remi GPG key with
#rpm --import http://rpms.famillecollet.com/RPM-GPG-KEY-remi
# cd /etc/yum.repos.d # wget http://rpms.famillecollet.com/enterprise/remi.repo
This file provides configuration for remi and remi-test repositories. Keep in mind that Remi repo is disabled by default so you can add –enablerepo=remi to yum command or you can edit line enabled=0 to enabled=1 inside remo.repo. For production servers I don’t recommend enabled=1 to remi-test repo.
Current PHP is 5.3.3 and MySQL 5.1.50