Problems with properties in object-oriented PHP

Class play{

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

}

Please ask the Public function callback (event $event) in the $event before why add event? What is the purpose 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();    ...}

}

Please ask the Public function callback (event $event) in the $event before why add event? What is the purpose of the event here?

Thank you

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

Thank you, that's the PHP parameter type limit for the function. That is, when you call $play->callback($event) , if $event it is not event the type, it will be an error. A table of PHP types can be set with a slice being a function parameter.

The input type is strictly restricted.

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