Attributes in php object-oriented

Classplay {code...} I 'd like to ask you why do you need to add an event before $ event in publicfunctioncallback (event $ event? What is the role of the event here? Thank you, class play {

private $message = null;public function __construct(){}public function callback(event $event){    $this->message = $event->click();    ...}

}

In public function callback (event $ event), why should we add an event before $ event? What is the role of the event here?

Thank you.

Reply content:

Class play {

private $message = null;public function __construct(){}public function callback(event $event){    $this->message = $event->click();    ...}

}

In public function callback (event $ event), why should we add an event before $ event? What is the role of the event here?

Thank you.

Type Declaration: The parameter $ event must be an instance of the (class/interface) event instance or a subclass of the event (or a class that implements the event interface ).

Thank you!PHPFunction parameter type restrictions. That is, when you call$play->callback($event)If$eventNoeventType. Slice isPHPFunction parameters can be used to set the type table.

Strictly limit the Input type.