gistfile1.php

<?php

class Currency {
    private $value = 0;
    
    public function setValue($value)
    {
        $this->value = $value;
    }
    
    public function getValue()
    {
        return $this->value;
    }
}

// This is the decorator.
class USCurrency {
    private $currency;
    
    public function __construct(Currency $currency)
    {
        $this->currency = $currency;
    }
    
    public function formatValue()
    {
        setlocale(LC_MONETARY, 'en_US');
        return money_format('%n', $this->currency->getValue());
    }
}