For all of you out there who are writing PHP code, I suggest reading Writing secure PHP and its part 2 by Dave.

I also strongly recommend using something like the quote_smart-function described in the PHP documentation (scroll down to example 3) when saving user input in the database.

The importance of writing secure code cannot be emphasized enough. Even if you’re writing a helper application for yourself someone, somewhere might try to crack it. And practising secure programming in even small projects will help you when you work on larger and more important projects. It’s all about the discipline.