a better way to upgrade rhel

Per LP519547, we have just pushed php52-suhosin and php53-suhosin to our el5-stable repositories for Red Hat Enterprise Linux 5 and clones.

Suhosin is an advanced protection system for PHP installations. It was designed to protect servers and users from known and unknown flaws in PHP applications and the PHP core. Suhosin comes in two independent parts, that can be used separately or in combination. The first part is a small patch against the PHP core, that implements a few low-level protections against bufferoverflows or format string vulnerabilities and the second part is a powerful PHP extension that implements all the other protections.

The packages pushed to IUS only implement the extension and not the core PHP patches.  Whether or not you should use Suhosin is up to you, but you may wish to read the Why? section on their site first.