Summary

In this chapter, we tried to explain the common programming paradigms used in most programming languages. These were: imperative, declarative and functional programming. We also compared the meanings of asynchronous and parallel code.

We spent some time on practical examples of functional programming in PHP and its downsides, and we went through examples of some not very common features, such as the Closure class.

Then, we examined the definition of reactive programming and how it's related to all we saw previously in this chapter.

We introduced Reactive Extensions (Rx) as a library for one of the possible approaches to reactive programming.

In two examples of RxJS, we saw what working with Reactive Extensions looks like in practice and how this matches our definition of reactive programming.

Finally, we introduced RxPHP, which we'll use throughout this entire book. We also quickly talked about differences between RxPHP 1.x and RxPHP 2.

In the next chapter, we'll have a closer look at various parts of the RxPHP library and talk more about the principles used in Reactive Extensions.