On DevShed today, there's a new tutorial posted looking at two things that can cause headaches for PHP developers (especially when evaluating and comparing values) - nulls and empty strings.
Anyone who has programmed for any length of time has encountered the concepts of null and empty strings. They are not the same, and confusing the two can cause some serious problems. This article deals with these concepts in the context of PHP and MySQL.
They start with a bit of a quiz before getting into how to handle them correctly - making null "safe" and working with it correctly in a MySQL context. SQL statements and table structures are included for their examples.