Events

Often when working with complex code bases, we may implement hooks and handlers so that our application can call custom code outside our main application flow. In Yii2, these handlers are called events, which can be automatically executed when a given event is triggered. For example, in a blogging platform, we may create an event to indicate that a post was published, which will trigger some custom code to send out an email to users in a specific mailing list. In this section, we'll cover how to create event handlers, trigger events, and write our own custom events.

Event handlers

Events in Yii2 are implemented within the yii\base\Component base class, which nearly every class in Yii2 extends from. By extending from this class, we can bind an event to nearly anywhere in our codebase. To begin working with events, we first need to create an event handler.

Event handlers in Yii2 can be bound by calling the yii\base\Component::on() method, and they specify a callback that should be executed...