Chapter 1. Introduction to Reactive Programming

Reactive programming has become a very popular and in demand topic over the last few years, and even though the ideas behind it aren't new, it takes the good parts from multiple different programming paradigms. This book's purpose is to teach you how to start writing PHP applications with principles of reactive programming in mind and in combination with pre-existing libraries.

In this chapter, we'll learn the most important principles that will guide us throughout this entire book:

• Recap well-known programming paradigms and quickly explain their meaning for humans.
• We'll see how we can use functional PHP programming, even today, using practical examples. We pay special attention to how we can use anonymous functions.
• Explain what reactive programing is and what good parts it takes from other programming paradigms.
• We'll have a look at some examples of widely spread JavaScript and PHP libraries that already use very similar principles to reactive programming.
• Introduce Reactive Extensions and see how these fit into the world of reactive programming.
• Show what using Reactive Extensions looks like using RxJS and how it fits into the grand scheme of things.
• Create a first simple demo with RxPHP library.

Since reactive programming is a programming paradigm, we'll take a quick look at other common paradigms that all of us have probably already heard of and that you'll see mentioned every time you read or hear about reactive programming.