oss android上传文件自定义签名一直错误求解

$str = "POST" . "n"

        . "
        \n"
        . "
        \n"
        . gmdate('D j M Y H:i:s', time() + 3600 * 8) . " GMT\n"
        . "/onshop/header/";

return base64_encode(hash_hmac('sha1', $str, $this->key, true));
这是php端的，

OSSCredentialProvider credentialProvider = new OSSCustomSignerCredentialProvider() {

        @Override
        public String signContent(String s) {
            Log.e("sign",sign);
            return "Authorization: OSS" + "kFuxGGMlJbiYQi8U" + ":" + sign;
        }
    };

这是安卓端的，求解决