$currency = new Currency();
  print_r($currency->convert('USD', 'JPY', 100));

Array ( [currency] => USDJPY [rate] => 85.995 [date] => 12/28/2012 [time] => 5:55pm [value] => 85.995 )

<?php
 
class Currency {
 
    public function __construct() {
 
    }
 
    public function convert($from='USD', $to='GBP', $amount=null) {
 
        $url = 'http://finance.yahoo.com/d/quotes.csv?e=.csv&f=sl1d1t1&s=' . $from . $to . '=X';
        $handle = @fopen($url, 'r');
        if ($handle) {
            $result = fgets($handle, 4096);
            fclose($handle);
        }
        $result = preg_replace('/"/', '', $result);
        $array = explode(',', $result);
 
        $ret = array('currency' => substr($array[0], 0, strlen($array[0]) - 2),
                    'rate' => $array[1],
                    'date' => $array[2],
                    'time' => $array[3]);
        if($amount != null) {
            $ret['value'] = $amount * ($array[1] / 100.0);
        }
        return $ret;
    }
 
}
 
//  $currency = new Currency();
//  print_r($currency->convert('USD', 'JPY', 100));
 
 
?>