i just got my dedicated server. i requested linux with Centos 5 on it. now im trying to install phpmyadmin into my server to manage my databases, but when i go through the installation it says:

phpMyAdmin

PHP 5.2+ is required

i check my php version and it says:
PHP 5.1.6 (cli) (built: Apr 7 2009 08:00:04)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies

so i tried updating it with yum:
yum update php

but i get this:
Excluding Packages from CentOS-5 - Base
Finished
Excluding Packages from CentOS-5 - Updates
Finished
Excluding Packages from CentOS-5 - Addons
Finished
Excluding Packages from CentOS-5 - Extras
Finished
Setting up Update Process
No Packages marked for Update

what can i do?