public static function exchange($amount, $from = 'NZD', $to = 'CNY')
 {
     $url = "http://www.google.com/finance/converter?a={$amount}&from={$from}&to={$to}";
     if ($data = RPC::fetch($url)) {
         $dom = new \DOMDocument();
         @$dom->loadHTML($data);
         $finder = new \DomXPath($dom);
         $classname = "bld";
         $nodes = $finder->query("//*[contains(concat(' ', normalize-space(@class), ' '), ' {$classname} ')]");
         $node = $nodes->item(0)->nodeValue;
         $amount = str_replace(' CNY', '', $node);
         return number_format($amount, 2, '.', ',');
     }
     return false;
 }