I have these requisite rpms installed (under Red Hat 5.7 server):

$ rpm -qa|grep php
php53-mbstring-5.3.3-26.el5_11
php53-mysql-5.3.3-26.el5_11
php53-cli-5.3.3-26.el5_11
php53-bcmath-5.3.3-26.el5_11
php53-pdo-5.3.3-26.el5_11
php53-gd-5.3.3-26.el5_11...