使用Amazon API MWS创建一个签名查询

我试图为卖家亚马逊网络服务(MWS)发出签名请求。我从这里使用一个脚本:将amazon MWS scratchpad查询转换为API调用

但我不知道为什么我有一个错误:"我们计算的请求签名与您提供的签名不匹配。检查您的AWS秘密访问密钥和签名方法。有关详细信息，请参阅服务文档。"

这是我的脚本:

define ("AWS_ACCESS_KEY_ID", "xxxxx");
define ("MERCHANT_ID", "xxxxx");
define ("MARKETPLACE_ID", "xxxxx");
define ("AWS_SECRET_ACCESS_KEY","xxxxx");
$base_url = "https://mws.amazonservices.fr/Products/2011-10-01";
$method = "POST";
$host = "mws.amazonservices.fr";
$uri = "/Products/2011-10-01";
function amazon_xml($searchTerm) {
$params = array(
'AWSAccessKeyId' => AWS_ACCESS_KEY_ID,
'Action' => "GetLowestOfferListingsForSKU",
'SellerId' => MERCHANT_ID,
'SignatureMethod' => "HmacSHA256",
'SignatureVersion' => "2",
'Timestamp'=> date("Y-m-d'TH:i:s.''0''0''0''Z", time()),
'Version'=> "2011-10-01",
'MarketplaceId' => MARKETPLACE_ID,
'Query' => $searchTerm,
'ItemCondition'=> "New",
'ExcludeMe' => "false");

// Sort the URL parameters
$url_parts = array();
foreach(array_keys($params) as $key)
$url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key]));
sort($url_parts);
// Construct the string to sign
$url_string = str_replace("%7E", "~", implode("&", $url_parts));
$string_to_sign = "POST'nmws.amazonservices.fr'n/Products/2011-10-01'n" . $url_string;
// Sign the request
$signature = hash_hmac('sha256', $string_to_sign, AWS_SECRET_ACCESS_KEY, TRUE);
// Base64 encode the signature and make it URL safe
$signature = rawurlencode(base64_encode($signature));
$url = "https://mws.amazonservices.fr/Products/2011-10-01" . '?' . $url_string . "&Signature=" . $signature;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, 15);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
$response = curl_exec($ch);
$parsed_xml = simplexml_load_string($response);
return ($parsed_xml);
}

我不明白出了什么问题如果有人能帮忙....

$url_parts = array();
foreach(array_keys($params) as $key)
    $url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key]));
sort($url_parts);
// Construct the string to sign
$url_string = implode("&", $url_parts);
$string_to_sign = "GET'nmws.amazonservices.com'n/Products/2011-10-01'n" . $url_string;
// Sign the request
$signature = hash_hmac("sha256", $string_to_sign, AWS_SECRET_ACCESS_KEY, TRUE);
// Base64 encode the signature and make it URL safe
$signature = urlencode(base64_encode($signature));
$url = "https://mws.amazonservices.com/Products/2011-10-01" . '?' . $url_string . "&Signature=" . $signature;