fetch item details and track listing from Amazon for an ASIN

amazon-track-lookup.php

<?php

// documentation: http://developer.amazonwebservices.com/connect/kbcategory.jspa?categoryID=19

ini_set('arg_separator.output', '&'); // for http_build_query

class Amazon {
  // Fill these in; the associate tag is optional
  public $key = ''; // https://aws-portal.amazon.com/gp/aws/developer/account/index.html?action=access-key
  public $secret = ''; // https://aws-portal.amazon.com/gp/aws/developer/account/index.html?action=access-key
  public $tag = ''; // https://affiliate-program.amazon.com/

  public $host = 'ecs.amazonaws.com';
  private $path = '/onca/xml';

  function sign($params){
    uksort($params, 'strnatcmp');
    foreach ($params as $key => &$value)
      $value = $key . '=' . rawurlencode($value); // http_build_query uses urlencode rather than rawurlencode

    return base64_encode(hash_hmac('sha256', implode("\n", array('GET', $this->host, $this->path, implode('&', $params))), $this->secret, TRUE));
  }

  function lookup($asin) {
    $params = array(
      'Service' => 'AWSECommerceService',
      'Version' => '2009-10-01',
      'Timestamp' => date(DATE_ISO8601),
      'AWSAccessKeyId' => $this->key,
      'AssociateTag' => $this->tag,
      'Operation' => 'ItemLookup',
      'IdType' => 'ASIN',
      'ItemId' => $asin,
      'ResponseGroup' => 'ItemAttributes,Images,Tracks',
      );

    $params['Signature'] = $this->sign($params);
    $xml = simplexml_load_file('http://' . $this->host . $this->path . '?' . http_build_query($params));

    if (!is_object($xml) || (string) $xml->Items->Request->IsValid != 'True')
      return array();
      
    $meta = NULL;
    if (!empty($xml->Items->Item)){
      $item = $xml->Items->Item;
      $tracks = array();
      foreach ($item->Tracks->Disc->Track as $track) // won't work properly with multiple discs; need to use DOM to cover those
        $tracks[] = (string) $track;

      $meta = array(
        'artist' => (string) $item->ItemAttributes->Artist,
        'title' => (string) $item->ItemAttributes->Title,
        'info' => (string) $item->DetailPageURL,
        'tracks' => $tracks,
        'images' => array(),
        );

      foreach (array('LargeImage', 'MediumImage', 'SmallImage') as $image)
        if (isset($item->{$image}))
          $meta['images'][$image] = (string) $item->{$image}->URL;
    }
    return $meta;
  }
}


$asin = 'B000003TA4';

$api = new Amazon;
$items = $api->lookup($asin);
print_r($items);

/*
  Array
  (
      [artist] => Nirvana
      [title] => Nevermind
      [info] => http://www.amazon.com/Nevermind-Nirvana/dp/B000003TA4...
      [tracks] => Array
          (
              [0] => Smells Like Teen Spirit
              [1] => In Bloom
              [2] => Come as You Are
              [3] => Breed
              [4] => Lithium
              [5] => Polly
              [6] => Territorial Pissings
              [7] => Drain You
              [8] => Lounge Act
              [9] => Stay Away
              [10] => On a Plain
              [11] => Something in the Way
          )

      [images] => Array
          (
              [LargeImage] => http://ecx.images-amazon.com/images/I/514q1roTpwL.jpg
              [MediumImage] => http://ecx.images-amazon.com/images/I/514q1roTpwL._SL160_.jpg
              [SmallImage] => http://ecx.images-amazon.com/images/I/514q1roTpwL._SL75_.jpg
          )

  )
*/