convert_amount_2_usd.php

<?php
/**
	 * Convert payment amount to USD currency in case the currency is not supported by the payment gateway
	 *
	 * @param $amount
	 * @param $currency
	 *
	 * @return float
	 */
	public static function convertAmountToUSD($amount, $currency)
	{
		static $rate = null;

		if ($rate === null)
		{
			$http     = JHttpFactory::getHttp();
			$url      = 'http://download.finance.yahoo.com/d/quotes.csv?e=.csv&f=sl1d1t1&s=USD' . $currency . '=X';
			$response = $http->get($url);

			if ($response->code == 200)
			{
				$currencyData = explode(',', $response->body);
				$rate         = floatval($currencyData[1]);
			}
		}

		if ($rate > 0)
		{
			$amount = $amount / $rate;
		}

		return round($amount, 2);
	}