Chapter 4. Reactive versus a Typical Event-Driven Approach

So far, we've been focused mainly on CLI applications. In this chapter, we'll apply what we've already learned to a typical component of all web frameworks, and add a little on top of that. We're going to use the Symfony EventDispatcher component, which is an independent library that can be used in any framework.

Its main purpose is dispatching events during an application's lifetime, and easy extendability. Most notably, it's a core building block of the Symfony3 framework and the Silex micro-framework.

In this chapter, we're going to do the following:

• Have a look at error handling in RxPHP and explain the retry(), retryWhen(), and catchError() operators. We'll see how these three relate to what we've talked about in the previous chapter.
• We'll see how to combine two Observables using concat() and merge() operators. Then we'll also have a look at concatMap...