find a track in Amazon's MP3 download store

amazon-track-lookup.php

<?php

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

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

    private $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($request) {
      $query = implode(' - ', array($request['artist'], $request['album'], $request['track']));

      $params = array(
        'Service' => 'AWSECommerceService',
        'Version' => '2009-10-01',
        'Timestamp' => date(DATE_ISO8601),
        'AWSAccessKeyId' => $this->key,
        'AssociateTag' => $this->tag,
        'Operation' => 'ItemSearch',
        'SearchIndex' => 'MP3Downloads',
        'ResponseGroup' => 'ItemAttributes,Images',
        'Keywords' => $query,
        );

      $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();

      $items = array();
      if (!empty($xml->Items->Item)){
        foreach ($xml->Items->Item as $item){
          $asin = (string) $item->ASIN;
          $attr = $item->ItemAttributes;

          $meta = array(
            'artist' => (string) $attr->Creator,
            'track' => (string) $attr->Title,
            'duration' => (string) $attr->RunningTime,
            'trackno' => (string) $attr->TrackSequence,
            'sample' => 'http://www.amazon.com/gp/dmusic/get_sample_url.html?ASIN=' . $asin,
            'info' => (string) $item->DetailPageURL,
            );

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

          $items[] = $meta;
        }
      }
      return $items;
    }
}

$api = new Amazon;
$items = $api->lookup(array('artist' => 'Nirvana', 'album' => 'Nevermind', 'track' => 'Smells Like Teen Spirit'));
print_r($items);

/*
Array
(
    [0] => Array
        (
            [artist] => Nirvana
            [track] => Smells Like Teen Spirit
            [duration] => 301
            [trackno] => 1
            [sample] => http://www.amazon.com/gp/dmusic/get_sample_url.html?ASIN=B000V639BK
            [info] => http://www.amazon.com/Smells-Like-Teen-Spirit/dp/B000V639BK%3FSubscriptionId%3Dexample%26tag%3D3Dexample%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB000V639BK
            [image] => http://ecx.images-amazon.com/images/I/51ntKGgKiDL.jpg
        )
[...]
*/