今天steam游戏开发时，游戏内置商店商品价格定价只有人民币（CNY）；而没有其他币种价格的设置，于是做了一个简单的货币兑换。
依照：百度汇率计算，修改了url参数

function rateAmount($currency, $price)
{
        //$baseCurrency:基本币种    $currency:转换币种
        //币种可识别中文和ISO 4217 currency code
        $query = urlencode('1' . $baseCurrency . '=' . $currency);
        $url = 'https://sp0.baidu.com/8aQDcjqpAAV3otqbppnN2DJv/api.php?query=' .
            $query .
            '&co=&resource_id=6017&t=' .
            time() * 1000 .
            '&cardId=6017&ie=utf8&oe=gbk&cb=op_aladdin_callback&format=json&tn=baidu&' .
            'cb=jQuery110209644633764682506_1534919455172&_=' .
            time() * 1000;
        $response = file_get_contents($url);
        //返回值是gbk格式的，转一下
        $response = iconv('GBK', 'UTF-8', $response);
        $json = substr($response, strpos($response, '(') + 1);
        $data = json_decode(substr($json, 0, -2), true);

        $result = $data['data'][0]['content1'];
        $rate = substr($result, strpos($result, '=') + 1, 5);
        //steam要求价格必须为整元且单位为分，比如1000而没有1050。
        $gameAmount = ceil($price / 100 * $rate) * 100;

        return (int)$gameAmount;
}

2. 上述方法总感觉差强人意，其他的一些基本上都要给钱或者次数限制；
   以下为steam官方api方法：
   文档地址：http://steam.steamlytics.xyz/api

function rateAmount($currency, $amount)
{
        $baseUrl = 'http://api.steam.steamlytics.xyz/v1/currencies/';
        $apiKey = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxx';

        $responseCurrencies = Cache::remember('currencies', 10, function () use ($baseUrl, $apiKey) {
            $url = $baseUrl . '?key=' . $apiKey;
            $response = $this->client->request('GET', $url);
            $json = json_decode($response->getBody(), true);

            return $json['currencies'];
        });

        $gameCurrencyId = 0;
        $currencyId = 0;

        foreach ($responseCurrencies as $id => $responseCurrency) {
            if ($responseCurrency['code'] == 'CNY') {
                $gameCurrencyId = $id;
            }

            if ($responseCurrency['code'] == $currency) {
                $currencyId = $id;
            }
        }

        $rateUrl = $baseUrl . 'convert/' . $amount . '/' . $gameCurrencyId . '/' .
            $currencyId . '?key=' . $apiKey;
        $rateResponse = $this->client->request('GET', $rateUrl);
        $data = json_decode($rateResponse->getBody(), true);

        $payAmount = $data['amount'];
}