<?php
 
interface MailTransport
{
	public function send($from, $to, $body);
}
 
class SendMail implements MailTransport
{
    public function send($from, $to, $body)
    {
        echo "sendmail";
    }
}
class Smtp implements MailTransport
{
    public function send($from, $to, $body)
    {
        echo "smtp";
 
    }
}
 
abstract class Mail
{
	protected $_transport;
	private $_body;
	private $_to;
 
	public function __construct(MailTransport $imp)
	{
		$this->_transport = $imp;
	}
 
}
class Notification extends Mail
{
	public function send()
	{
        $this->_transport->send();
	}
}
 
class Subscription extends Mail
{
 
	public function send()
	{
        $this->_transport->send();
	}
}
 
$mail = new Subscription(new SendMail());
$mail->send();
?>