DevShed has posted the next to last article in their validation helper series - a look at the full validation class in action checking various kinds of user input.

The functionality of each method of this class was based mostly on PHP filters, since this extension not only permits you to perform a decent validation on incoming data, but it makes this a no-brainer process. [...] In this tutorial I'm going to develop some basic examples that will illustrate the real capabilities of the class for verifying all the types of data mentioned above.

They include sample code checking two main kinds of user data - integers and floats and alphabetic/alphanumeric values as well as IP addresses, emails and URLs.