Book Image

PHP Reactive Programming

By : Martin Sikora
Book Image

PHP Reactive Programming

By: Martin Sikora

Overview of this book

Reactive Programming helps us write code that is concise, clear, and readable. Combining the power of reactive programming and PHP, one of the most widely used languages, will enable you to create web applications more pragmatically. PHP Reactive Programming will teach you the benefits of reactive programming via real-world examples with a hands-on approach. You will create multiple projects showing RxPHP in action alone and in combination with other libraries. The book starts with a brief introduction to reactive programming, clearly explaining the importance of building reactive applications. You will use the RxPHP library, built a reddit CLI using it, and also re-implement the Symfony3 Event Dispatcher with RxPHP. You will learn how to test your RxPHP code by writing unit tests. Moving on to more interesting aspects, you will implement a web socket backend by developing a browser game. You will learn to implement quite complex reactive systems while avoiding pitfalls such as circular dependencies by moving the RxJS logic from the frontend to the backend. The book will then focus on writing extendable RxPHP code by developing a code testing tool and also cover Using RxPHP on both the server and client side of the application. With a concluding chapter on reactive programming practices in other languages, this book will serve as a complete guide for you to start writing reactive applications in PHP.
Table of Contents (18 chapters)
PHP Reactive Programming
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Handling error states in operator chains


If we go back to Chapter 2 Reactive Programming with RxPHP, and CURLObservable, we know that it emits onError when it wasn't able to download any data. The question is, what if we want to try downloading the URL again? And even more interestingly, repeat the failed attempt every few seconds.

Subscribing only to onError signals is simple with the second parameter to the subscribeCallback() method:

(new CURLObservable('https://example.com')) 
    ->subscribeCallback(null, function($e) { ... }); 

It's obvious that nesting another CURLObservable into onError handler is probably not an option. This is exactly what the retry() operator is designed for.

The retry() operator

When the retry() operator receives an onError signal, it captures it and tries to resubscribe to its source Observable. It takes as an argument the number of times it tries to resubscribe until it passes the error signal down the operator chain.

Let's rewrite the preceding...