Объяснение реализации Посетителя

visitorExample.php

<?php

class EmailSender implements SenderInterface
{
    # prev behavior
  
    public function accept(Visitor $visitor)
    {
        $visitor->visitSenderEmail($this);
    } 
}

class SmsSender implements SenderInterface
{
    # prev behavior
    
    public function accept(Visitor $visitor)
    {
        $visitor->visitSmsSender($this);
    } 
}