Ther germany located security company SektionEins, which is specialized on Webapplication and PHP security, has a freebie to offer: You can download or order a PHP Security poster. They even send it in format A0 for free to you within the EU (European Union). It is available in english and german.
I think this is a great opportunity for every PHP developer to get reminded on some things.
SektionEins is well known for its founder Stefan Esser who is successfully doing security research since years. A well known PHP extension, suhosin, is part of many PHP installments. Just recently the Month of the PHP Security has been announced for May 2010.