developer.com: On the Security of PHP, Part 1
"In the following sections, we will identify a number of causes that commonly lead to violations of the security of PHP scripts and ultimately the systems on which these scripts are executing. We will then develop some guidelines for strengthening the security of PHP and for writing secure code. ..."
"From a security perspective, environment variables and user input data really aren't very different. They all represent data of unknown origin that may be hostile. Therefore, their use should be minimized whenever possible and their content examined and filtered the rest of the time. ..." Despite the fact that PHP is designed with security in mind, a familiarity with its more dangerous aspects and conformance to common secure programming guidelines is essential to minimizing the possibility of security compromises. The aim of this document is to provide an overview of various security issues with PHP and to offer advice on secure PHP programming practices.