PHP client for Amazon's Product Advertising API

AmazonClient.php

<?php

date_default_timezone_set('UTC');

// Create keys at https://console.aws.amazon.com/iam/home?#security_credential

class AmazonClient {
	/** @var cURL */
	public $curl;

	public $debug = false;

	private $version;
	private $host;
	private $path = '/onca/xml'; // turn into a host-keyed array if needed

	private $config = array();

	// constructor
	public function __construct($host = 'webservices.amazon.com', $version = '2011-08-01') {
		$this->host = $host;
		$this->version = $version;

		$this->configure();

		$this->curl = curl_init();
		curl_setopt($this->curl, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($this->curl, CURLOPT_ENCODING, 'gzip');
		//curl_setopt($this->curl, CURLOPT_VERBOSE, true);
	}

	// GET request
	public function get($params = array()) {
		$params['AWSAccessKeyId'] = $this->config['access_key'];
		$params['AssociateTag'] = $this->config['associate_tag'][$this->host];
		$params['Version'] = $this->version;
		$params['Timestamp'] = date('c');
		$params['Service'] = 'AWSECommerceService';
		$params['Signature'] = $this->sign('GET', $params);

		$url = 'http://' . $this->host . $this->path . '?' . $this->build_query($params);

		if ($this->debug) {
			print "$url\n";
		}

		curl_setopt($this->curl, CURLOPT_URL, $url);

		return $this->exec();
	}

	// read configuration from ~/.config/amazon.ini
	protected function configure() {
		$configFile = getenv('HOME') . '/.config/amazon.ini';

		if (!file_exists($configFile)) {
			printf("Config file %s does not exist\n", $configFile);
			exit();
		}

		$this->config = parse_ini_file($configFile);

		foreach (array('access_key', 'access_secret') as $field) {
			if (!isset($this->config[$field])) {
				printf("Add %s to %s\n", $field, $configFile);
				exit();
			}
		}

		foreach (array('associate_tag') as $field) {
			if (!isset($this->config[$field][$this->host])) {
				printf("Add %s[%s] to %s\n", $field, $this->host, $configFile);
				exit();
			}
		}
	}

	// send the request and parse the response
	protected function exec() {
		$result = curl_exec($this->curl);
		$code = curl_getinfo($this->curl, CURLINFO_HTTP_CODE);

		switch ($code) {
			case 200:
				$dom = new DOMDocument;
				$dom->preserveWhiteSpace = false;
				$dom->loadXML($result);

				if ($this->debug) {
					$dom->formatOutput = true;
					print $dom->saveXML();
				}

				$xpath = new DOMXPath($dom);
				$xpath->registerNamespace('a', 'http://webservices.amazon.com/AWSECommerceService/' . $this->version);

				return $xpath;

			default:
				print "Error $code\n";
				print $result;
				return null;
		}
	}

	// build the request signature
	protected function sign($verb = 'GET', $params = array()) {
		ksort($params);
		$request = implode("\n", array($verb, $this->host, $this->path, $this->build_query($params)));
		$signature = hash_hmac('sha256', $request, $this->config['access_secret'], true);

		return base64_encode($signature);
	}

	// build the query string, using '%20' for spaces
	protected function build_query($params = array()) {
		return http_build_query($params, null, '&', PHP_QUERY_RFC3986);
	}
}

browse.php

<?php

require __DIR__ . '/AmazonClient.php';

$client = new AmazonClient;

$params = array(
	'Operation' => 'BrowseNodeLookup',
	'BrowseNodeId' => '154606011', // Kindle eBooks
	'ResponseGroup' => 'TopSellers,MostGifted,NewReleases',
);

$xpath = $client->get($params);

$sets = array();

foreach ($xpath->query('a:BrowseNodes/a:BrowseNode/a:TopItemSet') as $topItemSet) {
	$items = array();

	foreach ($xpath->query('a:TopItem', $topItemSet) as $topItem) {
		$items[] = array(
			'url' => $xpath->evaluate('string(a:DetailPageURL)', $topItem),
			'title' => $xpath->evaluate('string(a:Title)', $topItem),
			'author' => $xpath->evaluate('string(a:Author)', $topItem),
		);
	}

	$sets[] = array(
		'type' => $xpath->evaluate('string(a:Type)', $topItemSet),
		'items' => $items,
	);
}

//print_r($sets);

search.php

<?php

require __DIR__ . '/AmazonClient.php';

$client = new AmazonClient;

$params = array(
	'Operation' => 'ItemSearch',
	'BrowseNode' => '154606011', // Kindle eBooks
	'ResponseGroup' => 'ItemAttributes,Reviews,Similarities,EditorialReview,Images',
	'SearchIndex' => 'Books', // KindleStore
	'Sort' => 'reviewrank',
	//'Keywords' => $_GET['keywords'],
);

$items = array();

foreach (range(1, 10) as $page) {
	$params['ItemPage'] = $page;

	$xpath = $client->get($params);

	foreach ($xpath->query('a:Items/a:Item') as $item) {
		$itemAttributes = $xpath->query('a:ItemAttributes', $item)->item(0);
		
		$pages = $xpath->evaluate('number(a:NumberOfPages)', $itemAttributes);

		$items[] = array(
			'url' => $xpath->evaluate('string(a:DetailPageURL)', $item),
			'image' =>  $xpath->evaluate('string(a:LargeImage/a:URL)', $item),
			'reviews' =>  $xpath->evaluate('string(a:CustomerReviews/a:IFrameURL)', $item),
			'title' => $xpath->evaluate('string(a:Title)', $itemAttributes),
			'author' => $xpath->evaluate('string(a:Author)', $itemAttributes),
			'pages' =>  is_nan($pages) ? null : $pages,
		);
	}
}

//print_r($items);