I'm very new to server-administration, but I was thinking the task of updating PHP to 5.2+ should be relatively simple. Online I found that the following was allegedly sufficient to do this:

yum update php

But when I run this, the following is output:

[root@ip-XXX-XXX-XXX-XXX /]# php -v
PHP 5.1.6 (cli) (built: Jan 13 2010 17:13:05)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
[root@ip-XXX-XXX-XXX-XXX /]# yum update php
Loaded plugins: fastestmirror
Determining fastest mirrors
 * addons: p3plmirror02.prod.phx3.secureserver.net
 * base: p3plmirror02.prod.phx3.secureserver.net
 * extras: p3plmirror02.prod.phx3.secureserver.net
 * turbopanel-base: p3plmirror02.prod.phx3.secureserver.net
 * turbopanel-centos5: p3plmirror02.prod.phx3.secureserver.net
 * update: p3plmirror02.prod.phx3.secureserver.net
addons                       |  951 B     00:00
addons/primary               |  201 B     00:00
base                         | 2.1 kB     00:00
base/primary_db              | 1.6 MB     00:00
extras                       | 1.1 kB     00:00
extras/primary               | 107 kB     00:00
extras                         325/325
turbopanel-base              |  951 B     00:00
turbopanel-base/primary      |  72 kB     00:00
turbopanel-base                494/494
turbopanel-centos5           |  951 B     00:00
turbopanel-centos5/primary   | 2.1 kB     00:00
turbopanel-centos5             8/8
update                       | 1.9 kB     00:00
update/primary_db            | 463 kB     00:00
Setting up Update Process
No Packages marked for Update
[root@ip-XXX-XXX-XXX-XXX /]# php -v
PHP 5.1.6 (cli) (built: Jan 13 2010 17:13:05)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technolog
[root@ip-XXX-XXX-XXX-XXX /]# No Packages marked for Update
[root@ip-XXX-XXX-XXX-XXX /]# php -v
bash: No: command not found
[root@ip-XXX-XXX-XXX-XXX /]# [root@ip-XXX-XXX-XXX-XXX /]# php -v
bash: [root@ip-XXX-XXX-XXX-XXX: command not found
[root@ip-XXX-XXX-XXX-XXX /]# PHP 5.1.6 (cli) (built: Jan 13 2010 17:13:05)
bash: syntax error near unexpected token `('
[root@ip-XXX-XXX-XXX-XXX /]# Copyright (c) 1997-2006 The PHP Group
bash: syntax error near unexpected token `c'
[root@ip-XXX-XXX-XXX-XXX /]# Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
bash: syntax error near unexpected token `('
[root@ip-XXX-XXX-XXX-XXX /]#

My PHP version is 5.1.6 before, and after running the command. Am I being too naive here with this update process? Is there a more verbose route that is necessary for me to take?