DevShed rounds the final corner on their sanitizing user input series of tutorials with the eighth part, a look at filtering inputted strings to remove potentially dangerous issues.

In this part, I discuss how to use the filter extension for sanitizing strings in all sorts of clever manners. I'll show you how to encode quotes, low and high ASCII characters in literals, and remove them in the same easy manner. Doing this can help prevent SQL injections and XSS attacks when developing PHP applications.

Their code shows how to use the FILTER_SANITIZE_STRING, FILTER_FLAG_NO_ENCODE_QUOTES, FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH, FILTER_FLAG_ENCODE_LOW and FILTER_FLAG_ENCODE_HIGH filtering methods on a sample string or two and what they'd result in.