On Reddit.com there's a recent post that asks the question How do YOU sanitize input in your PHP applications?

I am developing some software for my high school using HTML, CSS, MySQL, and most importantly PHP. [...] So I pose this question, what is YOUR favorite way to sanitize input for inserting, updating, or selecting from a database? Also, is there any way you prefer to verify that input is of a certain type, and only of that type ie, if you're expecting an int or a string, how would you make sure you are receiving one?

Answers on the post touch on things like:

• parametrised queries for databases
• filter_var/filter_types
• Sanitized versus "database-safe"
• using PDO
• avoiding the false sense of security things like mysql_escape_string and mysql_real_escape_string