On his blog, Roshan Bhattarai shares a few tips on keeping your application safe by filtering user-submitted data.

Yesterday, I saw one of my friend was working on the the contact form and was filtering the user input data(posted variables) individually. He was using a function in PHP to filter the input and using tedious approach while calling the filtering function for each variables with coding each of them in single line . Today, I'm going to show you how can you filter the posted variables easily using callback function in PHP.

He shows how to create a filter_data function (for removing HTML embedded in the data) and how to implement it around your data. It could be extended pretty easily to do more than one filtering method to protect your information even more.