Install Php5.2.x with yum.
1. Enable development repositories on CentOS, but only for i386
http://wiki.centos.org/HowTos/PHP_5.1_To_5.2
2. Only for Test Enviorment, not recommend for Prod. 
$rpm –import http://www.jasonlitka.com/media/RPM-GPG-KEY-jlitka
# create /etc/yum.repos.d/utterramblings.repo
$vi /etc/yum.repos.d/utterramblings.repo
# paste the following lines
[utterramblings]
name=Jason's Utter Ramblings Repo
baseurl=http://www.jasonlitka.com/media/EL$releasever/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://www.jasonlitka.com/media/RPM-GPG-KEY-jlitka
$yum update php
http://www.jasonlitka.com/yum-repository/