What is the event of yii

Events

Events allow custom code to be "injected" to a specific execution point in existing code. Attach custom code to an event and the code will be automatically executed when the event is triggered. (Recommended learning: yiitutorial)

For example, the messageSent event can be triggered when the mail program object successfully sends a message. If you want to track successfully sent messages, you can attach the corresponding tracking code to the messageSent event.

Yii introduces a base class named yii\base\Component to support events. If a class needs to trigger events, it should inherit yii\base\Component or its subclasses.

Event Handlers

The event handler is a PHP callback function that will be executed when the event it is attached to is triggered. You can use one of the following callback functions:

PHP global function specified in string form, such as 'trim';

Object method specified in array form of object name and method name, such as [$object, $method] ;

Static class method specified in the form of an array of class name and method name, such as [$class, $method];

Anonymous function, such as function ($event) { ... }.

The format of the event handler is:

function ($event) {
    // $event 是 yii\base\Event 或其子类的对象
}

Through the $event parameter, the event handler obtains the following information about the event:

event name: event name

event sender: the object that calls the trigger() method

custom data: the data passed in when attaching the event handler, the default is empty, after Detailed description in the article

Attaching Event Handlers

Call the yii\base\Component::on() method to attach the handler to the event. Such as:

$foo = new Foo;

// 处理器是全局函数
$foo->on(Foo::EVENT_HELLO, 'function_name');

// 处理器是对象方法
$foo->on(Foo::EVENT_HELLO, [$object, 'methodName']);

// 处理器是静态类方法
$foo->on(Foo::EVENT_HELLO, ['app\components\Bar', 'methodName']);

// 处理器是匿名函数
$foo->on(Foo::EVENT_HELLO, function ($event) {
    //事件处理逻辑
});

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