The answer to this question depends on what your usage of PHP is. If you are using PHP only for your own server and only for your own scripts and applications, then you can judge for yourself, if you trust your code enough. In that case you most probably don’t need the Suhosin extension. Because most of it’s features are meant to protect servers against vulnerable programming techniques. However PHP is a very complex programming language with a lot of pitfalls that are often overseen during the development of applications. Even PHP core programmers are writing insecure code from time to time, because they did not know about a PHP pitfall. Therefore it is always a good idea to have Suhosin as your safety net. The Suhosin-Patch on the other hand comes with Zend Engine Protection features that protect your server from possible bufferoverflows and related vulnerabilities in the Zend Engine. History has shown that several of these bugs have always existed in previous PHP versions.
If you are not only running your own PHP scripts but are also hosting 3rd party PHP applications for yourself or even for possible customers, then you cannot trust the code quality of the PHP applications you use. Unfortunately it is a fact that the pitfalls of the PHP language are not widely known among programmers. Many of these pitfalls are also not documented in the PHP-Security books that have been released during the last year. This is mainly caused by the fact, that the books were written in a hurry to be the first in market and because most of these books were not written by security professionals but by PHP programmers. The worst of these books is the one by Oreilly which contains examples that might fix the problem described but introduces more dangerous vulnerabilities into your application.
Another common error in these books is that they spread the urban legend that the most dangerous problem within PHP “remote code inclusion vulnerabilities” can be fixed by disabling allow_url_fopen in the configuration (or allow_url_include in PHP 5.2.x). This information is simply wrong, because these configuration directives do NOT protect against attacks through
data:// URLs. Our Suhosin and the former Hardening-Patch are the only available protections that close all URL include attacks.
Summed up, it is your free choice to use Suhosin. If you want additional protection for your servers and your business, we can only recommend strongly that you use the extension and the patch. Always keep in mind that you are not only protecting yourself and your users, but also other people on the internet, that might get attacked by your server after it has been turned into a (Spam-/DDOS-)attack drone.