So in line with the SQL injection cheat sheet I posted a couple of days ago, here's a few more links regarding security and PHP, certainly a topic every PHP developer should read up on to ensure their applications and websites are not vulnerable to even the most basic attacks.

• Writing Secure PHP Series (Part 1 link)
• Chris Shiflet's site, in particular his articles, although dated are insightful. Writer of the Essential PHP Security book, one I'm intending on getting ASAP.
• Find more in this Stackoverflow post which is where I've thieved the above links from. Thought I'd post them here for my own reference though.