Setup PHP 5.2 on CentOS 5.x Easily

Setup The Yum Repository

vi /etc/yum.repos.d/CentOS-Testing.repo

Paste the Below in the New File you Created.

[c5-testing] 
name=CentOS-5 Testing
baseurl=http://dev.centos.org/centos/$releasever/testing/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://dev.centos.org/centos/RPM-GPG-KEY-CentOS-testing

Update PHP

yum update php*

Restart Apache

service httpd restart

To make sure you have PHP 5.2 installed do the below.

php -v