Functional programming is a paradigm that is present every year at conferences. The
JavaScript community is probably one of the first that approached the subject, but the topic is
now also discussed among the developers using various other languages such as Ruby,
Python, and Java.
PHP has most of the features that are needed to start using a functional approach for
development. You have no reason to be left on the side, which is why this book proposes to
teach you the fundamentals of functional programming.
If you are completely new to functional programming or you want to refresh your basics and
learn a bit about its history and benefits, I recommend that you start with the appendix. It is not
the first chapter of the book as the content is not directly related to PHP, but it will help you put
various topics in context and have a better idea of the topics covered in this book.