I tried compiling PHP 5.2 on CentOS but after so many tries I gave up. I was getting struck at compiling PHP with gd. And without gd it was useless. So I decided to yum and install the same.
By default if you use yum install php it will be install only php 4 series and not 5. In order to install version 5 I had to enable repo centosplus.
yum install php –enablerepo=centosplus
yum update php –enablerepo=centosplus
I came across another interesting repo for yum by kbsingh and after installing I was able to install a lot more. If you are interested please check out this website
Have fun !! 😉