mytharcher\sdk\alipay\Alipay::signParameters PHP Method

    function signParameters($params)
    {
        // 支付宝的签名串必须是未经过 urlencode 的字符串
        // 不清楚为何 PHP 5.5 里没有 http_build_str() 方法
        $paramStr = urldecode(http_build_query($params));
        switch (strtoupper(trim($this->config['sign_type']))) {
            case "MD5":
                $result = md5($paramStr . $this->config['key']);
                break;
            case "RSA":
            case "0001":
                $priKey = file_get_contents($this->config['private_key_path']);
                $res = openssl_get_privatekey($priKey);
                openssl_sign($paramStr, $sign, $res);
                openssl_free_key($res);
                //base64编码
                $result = base64_encode($sign);
                break;
            default:
                $result = "";
        }
        return $result;
    }