The following errata for CentOS-2 have been built and uploaded to the centos mirror:

RHSA-2005:838-01 Moderate: php security update

Files available:
php-4.1.2-2.3.i386.rpm
php-devel-4.1.2-2.3.i386.rpm
php-imap-4.1.2-2.3.i386.rpm
php-ldap-4.1.2-2.3.i386.rpm
php-manual-4.1.2-2.3.i386.rpm
php-mysql-4.1.2-2.3.i386.rpm
php-odbc-4.1.2-2.3.i386.rpm
php-pgsql-4.1.2-2.3.i386.rpm

More details are available from the RedHat web site at
https://rhn.redhat.com/errata/rh21as-errata.html

The easy way to make sure you are up to date with all the latest patches is to run:
# yum update