some.php

<?php

interface Bonus
{
    public function apply(Amount $amount): Amount;
}

class AbsoluteBonus implements Bonus
{
    public static function fromInt(int $value): self
    {  
    }
    
    public function apply(Amount $amount): Amount
    {
      return $amount->sub($this->value);
    }
}

class RelativeBonus implements Bonus
{
    public static function fromInt(int $value): self
    {  
    }
    
    public function apply(Amount $amount): Amount
    {
      return $amount->multiply($this->value / 100);
    }
}

class PaymentMode
{
    private ?Bonus $bonus;

    public function applyBonus(Amount $amount): Amount
    {
      if (null === $this->bonus) {
        return $amount;
      }
      
      return $this->bonus->apply($amount);
    }
}

class Order
{
    private PaymentMode $paymentMode;
    
    public function total(): Amount
    {
      return $this->paymentMode->applyBonus($this->getItemsTotal());
    }
}