Design Patterns in PHP and Laravel

© Kelt Dockins 2017

Kelt Dockins, Design Patterns in PHP and Laravel, 10.1007/978-1-4842-2451-9_22

22. Observer

Kelt Dockins¹ 

(1)Dolph, Arkansas, USA

$> git checkout observer

Intent

Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.¹

Applications

The observer pattern is used when you want objects to react to specific events on a subject object. When the subject changes, it notifies observers. This is one of the most popular patterns I will cover. In fact, PHP already has built-in interfaces for the observer pattern: SplSubject ² and SplObserver ³.

Abstract Structure

Figure 22-1. Abstract structure

• SplSubjectis an abstract class or interface. When using ...