amazon_api.php

 <?php if (!defined('BASEPATH')) exit('No direct script access allowed');

// -------------------------------------------------------------------------------------------------
/**
 * Amazon Product Advertising API library
 * 
 * This is a very basic libary allowing you to search the Amazon Product Advertising API
 *
 * Based on and inspired by original CI Amazon library by Zac G. (http://zgordon.org) and on code by Richard Cummings (http://richardcummings.info/the-request-must-contain-the-parameter-signature-quick-fix-for-your-php-rest-requests/)
 *
 * @package       CodeIgniter
 * @subpackage    Libraries
 * @author        prabintp <http://www.crashcoder.com/contact/>    
 * @version        2.0
 * @license        http://www.opensource.org/licenses/bsd-license.php BSD licensed.
 *
 */
// -------------------------------------------------------------------------------------------------


class Amazon_api
{
	
	 /* Your Amazon Access Key Id
         * @access private
         * @var string
         */
        var $public_key     = "<AMAZON ACCESS KEY ID>";
        
        /**
         * Your Amazon Secret Access Key
         * @access private
         * @var string
         */
        var $private_key    = "<AMAZON SECRET KEY>";
        
        /**
         * Your Amazon Associate Tag
         * @access private
         * @var string
         */
        var $associate_tag  = "<ASSOC TAG>";
    
       
        /*
            Only three categories are listed here. 
            More categories can be found here:
            http://docs.amazonwebservices.com/AWSECommerceService/latest/DG/APPNDX_SearchIndexValues.html
        */
      
       

    function Amazon_api()
    {
    
    }
function  aws_signed_request($region,$params,$public_key,$private_key,$associate_tag)
{

    $method = "GET";
    $host = "ecs.amazonaws.".$region; // must be in small case
    $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 thus
      failing the authetication 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 with SHA256 and base64-encoding.
       The 'hash_hmac' function is only available from PHP 5 >= 5.1.2.
    */
    $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 cURL doesn't work for you, then use the 'file_get_contents'
       function as given below.
    */
    
    if ($xml_response === False)
    {
        return False;
    }
    else
    {
        /* parse XML */
        $parsed_xml = @simplexml_load_string($xml_response);
        return ($parsed_xml === False) ? False : $parsed_xml;
    }
}

	      /**
         * Check if the xml received from Amazon is valid
         * 
         * @param mixed $response xml response to check
         * @return bool false if the xml is invalid
         * @return mixed the xml response if it is valid
         * @return exception if we could not connect to Amazon
         */
        private function verifyXmlResponse($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.");
                }
            }
        }
        
        
        /**
         * Query Amazon with the issued parameters
         * 
         * @param array $parameters parameters to query around
         * @return simpleXmlObject xml query response
         */
        private function queryAmazon($parameters)
        {
            return $this->aws_signed_request("com", $parameters, $this->public_key,$this->private_key, $this->associate_tag);
        }
        
        
        /**
         * Return details of products searched by various types
         * 
         * @param string $search search term
         * @param string $category search category         
         * @param string $searchType type of search
         * @return mixed simpleXML object
         */
        public function searchProducts($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);

        }
        
        
        /**
         * Return details of a product searched by UPC
         * 
         * @param int $upc_code UPC code of the product to search
         * @param string $product_type type of the product
         * @return mixed simpleXML object
         */
        public function getItemByUpc($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);

        }
        
        
        /**
         * Return details of a product searched by ASIN
         * 
         * @param int $asin_code ASIN code of the product to search
         * @return mixed simpleXML object
         */
        public function getItemByAsin($asin_code)
        {
            $parameters = array("Operation"     => "ItemLookup",
                                "ItemId"        => $asin_code,
                                "ResponseGroup" => "Medium");
                                
            $xml_response = $this->queryAmazon($parameters);
            
            return $this->verifyXmlResponse($xml_response);
        }
        
        
        /**
         * Return details of a product searched by keyword
         * 
         * @param string $keyword keyword to search
         * @param string $product_type type of the product
         * @return mixed simpleXML object
         */
        public function getItemByKeyword($keyword, $product_type)
        {
            $parameters = array("Operation"   => "ItemSearch",
                                "Keywords"    => $keyword,
                                "SearchIndex" => $product_type);
                                
            $xml_response = $this->queryAmazon($parameters);
            
            return $this->verifyXmlResponse($xml_response);
        }
     
}
?>