config.yml

---
Name: mysite
After:
  - 'framework/*'
  - 'cms/*'
---
# YAML configuration for SilverStripe
# See http://doc.silverstripe.org/framework/en/topics/configuration
# Caution: Indentation through two spaces, not tabs
SSViewer:
  theme: 'one-ring'
SiteConfig:
  extensions:
    - SiteConfigExtension
Currency:
  currency_symbol: 'DKK '
  extensions:
    - CurrencySymbol

CurrencySymbol.php

<?php
Class CurrencySymbol extends DataExtension {
	public function SymbolNice() {
		$val = number_format(abs($this->value) . $this->config()->currency_symbol, 2);
		if($this->value < 0) return "($val)";
		else return $val;
	}
}

HomePage.ss

<div class="price">
	<span>$PricePerNight.SymbolNice</span><p>per night<p>
</div>