Following up on a previous article, Stuart Herbert has posted some of the things that PHP can do to help solve the previously mentioned shared hosting problems.

The challenge is to secure the box not just from outside attack (something you have to do anyway, and which I’ll cover later in this series), but also to make sure that code running on one website can’t steal confidential data like MySQL passwords from any of the other websites.

It's not just a problem that PHP has, but it does, thankfully, have several settings and things that you can do to help. Among those on the list are things like: safe_mode, open_basedir and how PHP 6 will effect both of these. He's included settings for both of them to get you started.