The Standard PHP Library (SPL) is a powerful set of tools that are often overlooked. It is very common to see an SPL talk at conferences, but those talks usually just introduce each SPL class to the audience without giving some real world examples. I am going to show you a real world example on how to use SPL FilterIterator in an ecommerce website.
It has been said that all languages, over time, implement a dialect of lisp. PHP appears to be no exception.