yum install yum-priorities
rpm -import http://dev.centos.org/centos/RPM-GPG-KEY-CentOS-testing
cd /etc/yum.repos.d
wget http://dev.centos.org/centos/5/CentOS-Testing.repo
edit CentOS-Testing.repo, and set enabled=1
edit CentOS-Base.repo and exclude=php*
yum update