PHP OOP with Interface

Notif.php

<?php 

// INTERFACE

ini_set('display_startup_errors', 1);
ini_set('display_errors', 1);
error_reporting(-1);

interface Notif{
    public function send($message, $contacts);
}

class EmailNotif implements Notif{

    public function send($message, $contacts){
        $target = $contacts['email'];
        var_dump("EmailNotif : the message `".$message."` delivered to -> ".$target);
    }
}

class SMSNotif implements Notif{
    public function send($message, $contacts){
        $target = $contacts['number'];
        var_dump("SMSNotif : the message `".$message."` delivered to -> ".$target);
    }
}

class User{

    private $data = [];

    public function __construct($data){
        $this->data = $data;
    }

    public function send_notif(Notif $notifier){
        var_dump("User Class : let's send notif");
        $message = "you are registered successfully";
        $notifier->send($message, $this->data['contacts']);
    }
}

$registration_data = array(
    "name" => "marjuqi",
    "gender" => "male",
    "contacts" => array(
        "number" => "0812000000",
        "email" => "a@a.com"
    )
);

$user = new User($registration_data);
echo '<pre>';
$user->send_notif(new SMSNotif);
$user->send_notif(new EmailNotif);
echo '</pre>';

?>