Magento REST API：oauth_problem = signature_invalid

Question

以下代码会返回错误消息：

Invalid auth/bad request (got a 401, expected HTTP/1.1 20X or a redirect)
{"messages":{"error":[{"code":401,"message":"oauth_problem=signature_invalid"}]}}

有人知道解决方案吗？当我创建产品并尝试将其分配到某个类别时，就会发生这种情况。

try {
    $authType = ($_SESSION['state'] == 2) ? OAUTH_AUTH_TYPE_AUTHORIZATION : OAUTH_AUTH_TYPE_URI;
    $oauthClient = new OAuth($consumerKey, $consumerSecret, OAUTH_SIG_METHOD_HMACSHA1, $authType);
    $oauthClient->enableDebug();

//Creating the product here and straight after assiging it to a category

} catch (OAuthException $e) {
    print_r($e->getMessage());
    echo '<br/>';
    print_r($e->lastResponse);
}