OOP: Interfaces (abstract vs interface)

<?php


interface PaymentMethod {
  function pay();
  function status();
}

class CreditCard implements PaymentMethod{
    public function pay(){
      return "The payment is done by Credit Card.";
    }
     public function status(){
      return "The payment is successfully processed.";
    }

}

class UPI implements PaymentMethod{
   public function pay(){
      return "The payment is done by UPI.";
    }
     public function status(){
      return "The payment is successfully processed.";
    }
}

class NetBanking implements PaymentMethod{
   public function pay(){
      return "The payment is done by Net Banking.";
    }
     public function status(){
      return "The payment is successfully processed.";
    }
}

// this can be used with any class that implements PaymentMethod
function checkout(PaymentMethod $method){
   return $method->pay() . " " . $method->status();
}

echo checkout(new CreditCard());