New from NETTUTS.com today there's an article that both reminds PHP developers of the importance of filtering data and gives them a long list of the filters that PHP has to make it easy.

Data security is important and often undervalued by designers, developers, and clients alike. Since PHP 5.2.0, data sanitization and validation has been made significantly easier with the introduction of data filtering. Today, we're going to take a closer look at these filters, how to use them, and build a few custom functions.

They talk about filtering things like cross-site scripting, SQL injections and "improper" data in your submissions. They look at the filter extension and how the filter_var function can be used in combination with a long list of filter types to ensure the validity of your data (like FILTER_VALIDATE_EMAIL, FILTER_VALIDATE_IP, FILTER_SANITIZE_STRING and FILTER_SANITIZE_URL). They also briefly mention the use of custom functions to handle validation on more complex data sets.