php_interface_sample4.php

<?php

interface NotificationServiceInterface
{
    public function send(int $notificationCode);
}

class UserNotificationService implements NotificationServiceInterface
{
    //略
   
    public function send(int $notificationCode)
    {
        if (is_null($notificationCode)) {
            NormalUserNotification::notify();
            return;
        }

        foreach ($this->notifications as $notification) {
            if ($notification::code() === $notificationCode) {
                if ((new $notification) instanceof NotificationToAdminInterface) {
                    $this->sendToAdmin();
                }
                $notification::notify();
                return;
            }
        }

        throw new InvalidArgumentException();
    }
    
    private function sendToAdmin()
    {
        //logic
    }
}

interface NotificationInterface
{
    public static function code() : int;
    public static function notify();
}

interface NotificationToAdminInterface
{
//空のInterface
}

//略

class TypeBUserNotification implements NotificationToAdminInterface, NotificationInterface
{
    public static function code() : int
    {
    	return config('notification.type.b.value');
    }

    public static function notify()
    {
        //logic
    }
}