DevShed continues their look at filtering in PHP5 applications with this third part covering checks on boolean values.

As I said before, the filter extension can be used for more than validating integers, since it provides the required functionality to checking other data types. Thus, in the next few lines I'm going to discuss how to use the extension for validating Boolean values.

They give a few lines of example code to show how different values (like "1" versus 1 and "true" versus true) are affected by PHP's dynamic typing.