Today I had some trouble with a simple package update on CentOS.
The php version on the server was 5.1.6 while the current version is 5.2.6
And the update did nothing .. absolutely nothing it said that I have the latest version.

I found the solution to my problem here:

http://bluhaloit.wordpress.com/2008/03/13/installing-php-52x-on-redhat-es5-centos-5-etc/

Problem is, RedHat ES5 does not have support at this time for anything higher than 5.1.6, and we didn’t want to break RPM dependancys etc by installing from source.

To install PHP 5.2.5 (Highest in repository at this time) you can make use of a RPM repository maintained by Remi. He has a repository for each distro, but to save you translating for the ES5 one I’ll give you the commands here. Run the following to get up and running:

wget http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-2.noarch.rpm
wget http://rpms.famillecollet.com/el5.i386/remi-release-5-4.el5.remi.noarch.rpm
rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm

You now have the Remi repository on your system, however it is disabled by default. Obviously you don’t want all of your packages been effected by this repository, however to enable it for a specific package, run the following:

yum --enablerepo=remi update php