DevShed has posted a new tutorial today (the start of a series) looking at using the filtering extension that comes native with PHP5 versions to clean up any data the user might give you.

Definitely, one of the most common tasks that PHP programmers have to tackle during the development of web applications is validating user-supplied data. [...] The use of native PHP filters may contribute significantly to saving time and effort when it comes to validating input data. In this series of articles I’m going to attempt to provide you with a concise guide to how to use them, as usual by way of a decent variety of code samples.

He starts off by looking at some of the filters that are available and show how to use one of them in a specific example - checking for integer values in a given input string.