我在这个Amazon API代码中替换什么才能使它工作

我正在尝试使用此网站的代码从Amazon产品API获取输出。

它有三个部分：

1. 已签名的请求
2. api类
3. 查询

作为一个亚马逊联合体，我有3个值需要插入到代码中：

1. 关联标记
2. 公钥（通用密钥）
3. 私钥（密钥）

在API类中，插入这些值的位置很清楚：

require_once 'aws_signed_request.php';
class AmazonProductAPI
{
    private $public_key     = "YOUR AMAZON ACCESS KEY ID";
    private $private_key    = "YOUR AMAZON SECRET KEY";
    /* 'Associate Tag' now required, effective from 25th Oct. 2011 */
    private $associate_tag  = "YOUR AMAZON ASSOCIATE TAG";
    const MUSIC = "Music";
    const DVD   = "DVD";
    const GAMES = "VideoGames";
    private function verifyXmlResponse($response)
    {
        if ($response === False)
        {
            throw new Exception("Could not connect to Amazon");
        }
        else
        {
            if (isset($response->Items->Item->ItemAttributes->Title))
            {
                return ($response);
            }
            else
            {
                throw new Exception("Invalid xml response.");
            }
        }
    }
    private function queryAmazon($parameters)
    {
        return aws_signed_request("com",
                                  $parameters,
                                  $this->public_key,
                                  $this->private_key,
                                  $this->associate_tag);
    }
    public function searchProducts($search,$category,$searchType="UPC")
    {
        $allowedTypes = array("UPC", "TITLE", "ARTIST", "KEYWORD");
        $allowedCategories = array("Music", "DVD", "VideoGames");
        switch($searchType) 
        {
            case "UPC" :
                $parameters = array("Operation"     => "ItemLookup",
                                    "ItemId"        => $search,
                                    "SearchIndex"   => $category,
                                    "IdType"        => "UPC",
                                    "ResponseGroup" => "Medium");
                            break;
            case "TITLE" :
                $parameters = array("Operation"     => "ItemSearch",
                                    "Title"         => $search,
                                    "SearchIndex"   => $category,
                                    "ResponseGroup" => "Medium");
                            break;
        }
        $xml_response = $this->queryAmazon($parameters);
        return $this->verifyXmlResponse($xml_response);
    }
    public function getItemByUpc($upc_code, $product_type)
    {
        $parameters = array("Operation"     => "ItemLookup",
                            "ItemId"        => $upc_code,
                            "SearchIndex"   => $product_type,
                            "IdType"        => "UPC",
                            "ResponseGroup" => "Medium");
        $xml_response = $this->queryAmazon($parameters);
        return $this->verifyXmlResponse($xml_response);
    }
    public function getItemByAsin($asin_code)
    {
        $parameters = array("Operation"     => "ItemLookup",
                            "ItemId"        => $asin_code,
                            "ResponseGroup" => "Medium");
        $xml_response = $this->queryAmazon($parameters);
        return $this->verifyXmlResponse($xml_response);
    }
    public function getItemByKeyword($keyword, $product_type)
    {
        $parameters = array("Operation"   => "ItemSearch",
                            "Keywords"    => $keyword,
                            "SearchIndex" => $product_type);
        $xml_response = $this->queryAmazon($parameters);
        return $this->verifyXmlResponse($xml_response);
    }
}

但是这个API类最初使用的是签名请求。在签名请求中，我不知道在哪里插入这3个值：

<?php
function  aws_signed_request($region,
                             $params,
                             $public_key,
                             $private_key,
                             $associate_tag)
{
    $method = "GET";
    $host = "ecs.amazonaws.".$region;
    $uri = "/onca/xml";

    $params["Service"]          = "AWSECommerceService";
    $params["AWSAccessKeyId"]   = $public_key;
    $params["AssociateTag"]     = $associate_tag;
    $params["Timestamp"]        = gmdate("Y-m-d'TH:i:s'Z");
    $params["Version"]          = "2009-03-31";
    /* The params need to be sorted by the key, as Amazon does this at
      their end and then generates the hash of the same. If the params
      are not in order then the generated hash will be different from
      Amazon thus failing the authentication process.
    */
    ksort($params);
    $canonicalized_query = array();
    foreach ($params as $param=>$value)
    {
        $param = str_replace("%7E", "~", rawurlencode($param));
        $value = str_replace("%7E", "~", rawurlencode($value));
        $canonicalized_query[] = $param."=".$value;
    }
    $canonicalized_query = implode("&", $canonicalized_query);
    $string_to_sign = $method."'n".$host."'n".$uri."'n".
                            $canonicalized_query;
    /* calculate the signature using HMAC, SHA256 and base64-encoding */
    $signature = base64_encode(hash_hmac("sha256", 
                                  $string_to_sign, $private_key, True));
    /* encode the signature for the request */
    $signature = str_replace("%7E", "~", rawurlencode($signature));
    /* create request */
    $request = "http://".$host.$uri."?".$canonicalized_query."&Signature=".$signature;
    /* I prefer using CURL */
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$request);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_TIMEOUT, 15);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    $xml_response = curl_exec($ch);
    if ($xml_response === False)
    {
        return False;
    }
    else
    {
        /* parse XML and return a SimpleXML object, if you would
           rather like raw xml then just return the $xml_response.
         */
        $parsed_xml = @simplexml_load_string($xml_response);
        return ($parsed_xml === False) ? False : $parsed_xml;
    }
}
?>