Oracle have just released a set of PHP RPMs for Oracle which include OCI8 and Oracle PDO driver, as well as many other PHP extensions. I think this is great, even it’s for development testing only and not supported by Oracle. The RPMs are based on PHP 5.2.3, according to the blog post by Alison Holloway from Oracle.
RPMs can be downloaded from http://oss.oracle.com/projects/php/, to install the PHP OCI8 you will need to install the Oracle’s free Instant Client Basic package and PHP’s php-pdo package :
1- as root run :

rpm -ivh php-common-5.2.3-1.i386.rpm php-cli-5.2.3-1.i386.rpm php-5.2.3-1.i386.rpm

2- Download oracle-instantclient-basic-10.2.0.3-1.i386.rpm and install it

rpm -ivh oracle-instantclient-basic-10.2.0.3-1.i386.rpm

3- Install PHP’s PDO extension :

rpm -ivh php-pdo-5.2.3-1.i386.rpm

4- Install PHP’s Oracle OCI8 and PDO_OCI extensions :

rpm -ivh php-oci8-5.2.3-1.i386.rpm