Download the RPMs you require for your new PHP installation from the following URLs. If you have RPMs that aren’t listed, use the search function:

php-5.2.5

pcre-6.6
php-cli-5.2.5
php-common-5.2.5
php-pear-1.7.1
php-gd-5.2.5
php-pd-5.2.5
php-mysql-5.2.5
sqllite

Or if you are upgrading another distrobution, search for the equivalents here.
Check which PHP RPMs you currently have installed:
rpm -qa | grep phpphp-5.1.6-1.6
Output should be something like:
php-pear-1.4.9-1.2

php-pdo-5.1.6-1.6

php-gd-5.1.6-1.6

php-mysql-5.1.6-1.6
** Do The Following [...]