The Zend Developer Zone has the latest two of their security tips posted today - numer #8 and #9 - in their "PHP Security Tips" series.

• In tip #8, they restate and reinforce a topic that's worth repeating - validating user input. They use the filter_var function as a simple, light way to start filtering your user's input.
• Tip #9 suggests that you keep anything sensitive, anything at all that needs to be kept away from prying eyes, outside of your document root of the site.