Codeigniter Amazon MWS Payments Login With Amazon / Login and Pay With Amazon API Method Caller - Their SDK Sucks

CI_MWSPayments

	//amazon's api is a real pain in the rear
	private function _amazonRequest($action, $params){		
		$base = array(
			'Action' => $action,
			'Timestamp' => date("Y-m-d\TH:i:s.\\0\\0\\0\\Z", time()),
			'AWSAccessKeyId' => $this->amazon['accessKey'],
			'SignatureVersion' => 2,
			'SignatureMethod' => 'HmacSHA256',
			'SellerId' => $this->amazon['sellerId'],
			'Version' => '2013-01-01'
		);
		
		$params = array_merge($base, $params);

		$url_parts = array();
		foreach(array_keys($params) as $key)
			$url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key]));
		sort($url_parts);

		// Construct the string to sign
		$url_string = implode("&", $url_parts);
		$string_to_sign = "GET\nmws.amazonservices.com\n/OffAmazonPayments_Sandbox/2013-01-01\n" . $url_string;

		// Sign the request
		$signature = hash_hmac("sha256", $string_to_sign, $this->amazon['secretKey'], TRUE);

		// Base64 encode the signature and make it URL safe
		$signature = urlencode(base64_encode($signature));

		return simplexml_load_file($this->amazon['sandbox'].'?'.$url_string."&Signature=".$signature);
	}