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 <?php
 /**
  * Zend Framework
  *
  * LICENSE
  *
  * This source file is subject to the new BSD license that is bundled
  * with this package in the file LICENSE.txt.
  * It is also available through the world-wide-web at this URL:
  * http://framework.zend.com/license/new-bsd
  * If you did not receive a copy of the license and are unable to
  * obtain it through the world-wide-web, please send an email
  * to license@zend.com so we can send you a copy immediately.
  *
  * @category   Zend
  * @package    Zend_Feed_Pubsubhubbub
  * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  * @version    $Id$
  */
 
 /**
  * @see Zend_Feed_Pubsubhubbub
  */
 // require_once 'Zend/Feed/Pubsubhubbub.php';
 
 /**
  * @see Zend_Date
  */
 // require_once 'Zend/Date.php';
 
 /**
  * @category   Zend
  * @package    Zend_Feed_Pubsubhubbub
  * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  */
 class Zend_Feed_Pubsubhubbub_Subscriber
 {
     /**
      * An array of URLs for all Hub Servers to subscribe/unsubscribe.
      *
      * @var array
      */
     protected $_hubUrls = array();
 
     /**
      * An array of optional parameters to be included in any
      * (un)subscribe requests.
      *
      * @var array
      */
     protected $_parameters = array();
 
     /**
      * The URL of the topic (Rss or Atom feed) which is the subject of
      * our current intent to subscribe to/unsubscribe from updates from
      * the currently configured Hub Servers.
      *
      * @var string
      */
     protected $_topicUrl = '';
 
     /**
      * The URL Hub Servers must use when communicating with this Subscriber
      *
      * @var string
      */
     protected $_callbackUrl = '';
 
     /**
      * The number of seconds for which the subscriber would like to have the
      * subscription active. Defaults to null, i.e. not sent, to setup a
      * permanent subscription if possible.
      *
      * @var int
      */
     protected $_leaseSeconds = null;
 
     /**
      * The preferred verification mode (sync or async). By default, this
      * Subscriber prefers synchronous verification, but is considered
      * desireable to support asynchronous verification if possible.
      *
      * Zend_Feed_Pubsubhubbub_Subscriber will always send both modes, whose
      * order of occurance in the parameter list determines this preference.
      *
      * @var string
      */
     protected $_preferredVerificationMode
         = Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC;
 
     /**
      * An array of any errors including keys for 'response', 'hubUrl'.
      * The response is the actual Zend_Http_Response object.
      *
      * @var array
      */
     protected $_errors = array();
 
     /**
      * An array of Hub Server URLs for Hubs operating at this time in
      * asynchronous verification mode.
      *
      * @var array
      */
     protected $_asyncHubs = array();
 
     /**
      * An instance of Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface used to background
      * save any verification tokens associated with a subscription or other.
      *
      * @var Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface
      */
     protected $_storage = null;
 
     /**
      * An array of authentication credentials for HTTP Basic Authentication
      * if required by specific Hubs. The array is indexed by Hub Endpoint URI
      * and the value is a simple array of the username and password to apply.
      *
      * @var array
      */
     protected $_authentications = array();
 
     /**
      * Tells the Subscriber to append any subscription identifier to the path
      * of the base Callback URL. E.g. an identifier "subkey1" would be added
      * to the callback URL "http://www.example.com/callback" to create a subscription
      * specific Callback URL of "http://www.example.com/callback/subkey1".
      *
      * This is required for all Hubs using the Pubsubhubbub 0.1 Specification.
      * It should be manually intercepted and passed to the Callback class using
      * Zend_Feed_Pubsubhubbub_Subscriber_Callback::setSubscriptionKey(). Will
      * require a route in the form "callback/:subkey" to allow the parameter be
      * retrieved from an action using the Zend_Controller_Action::_getParam()
      * method.
      *
      * @var string
      */
     protected $_usePathParameter = false;
 
     /**
      * Constructor; accepts an array or Zend_Config instance to preset
      * options for the Subscriber without calling all supported setter
      * methods in turn.
      *
      * @param  array|Zend_Config|null $config Options array or Zend_Config instance
      * @throws Zend_Feed_Pubsubhubbub_Exception
      */
     public function __construct($config = null)
     {
         if ($config !== null) {
             $this->setConfig($config);
         }
     }
 
     /**
      * Process any injected configuration options
      *
      * @param  array|Zend_Config $config Options array or Zend_Config instance
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setConfig($config)
     {
         if ($config instanceof Zend_Config) {
             $config = $config->toArray();
         } elseif (!is_array($config)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Array or Zend_Config object'
                 . ' expected, got ' . gettype($config));
         }
         if (array_key_exists('hubUrls', $config)) {
             $this->addHubUrls($config['hubUrls']);
         }
         if (array_key_exists('callbackUrl', $config)) {
             $this->setCallbackUrl($config['callbackUrl']);
         }
         if (array_key_exists('topicUrl', $config)) {
             $this->setTopicUrl($config['topicUrl']);
         }
         if (array_key_exists('storage', $config)) {
             $this->setStorage($config['storage']);
         }
         if (array_key_exists('leaseSeconds', $config)) {
             $this->setLeaseSeconds($config['leaseSeconds']);
         }
         if (array_key_exists('parameters', $config)) {
             $this->setParameters($config['parameters']);
         }
         if (array_key_exists('authentications', $config)) {
             $this->addAuthentications($config['authentications']);
         }
         if (array_key_exists('usePathParameter', $config)) {
             $this->usePathParameter($config['usePathParameter']);
         }
         if (array_key_exists('preferredVerificationMode', $config)) {
             $this->setPreferredVerificationMode(
                 $config['preferredVerificationMode']
             );
         }
         return $this;
     }
 
     /**
      * Set the topic URL (RSS or Atom feed) to which the intended (un)subscribe
      * event will relate
      *
      * @param  string $url
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setTopicUrl($url)
     {
         if (empty($url) || !is_string($url) || !Zend_Uri::check($url)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "url"'
                 .' of "' . $url . '" must be a non-empty string and a valid'
                 .' URL');
         }
         $this->_topicUrl = $url;
         return $this;
     }
 
     /**
      * Set the topic URL (RSS or Atom feed) to which the intended (un)subscribe
      * event will relate
      *
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return string
      */
     public function getTopicUrl()
     {
         if (empty($this->_topicUrl)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('A valid Topic (RSS or Atom'
                 . ' feed) URL MUST be set before attempting any operation');
         }
         return $this->_topicUrl;
     }
 
     /**
      * Set the number of seconds for which any subscription will remain valid
      *
      * @param  int $seconds
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setLeaseSeconds($seconds)
     {
         $seconds = intval($seconds);
         if ($seconds <= 0) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Expected lease seconds'
                 . ' must be an integer greater than zero');
         }
         $this->_leaseSeconds = $seconds;
         return $this;
     }
 
     /**
      * Get the number of lease seconds on subscriptions
      *
      * @return int
      */
     public function getLeaseSeconds()
     {
         return $this->_leaseSeconds;
     }
 
     /**
      * Set the callback URL to be used by Hub Servers when communicating with
      * this Subscriber
      *
      * @param  string $url
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setCallbackUrl($url)
     {
         if (empty($url) || !is_string($url) || !Zend_Uri::check($url)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "url"'
                 . ' of "' . $url . '" must be a non-empty string and a valid'
                 . ' URL');
         }
         $this->_callbackUrl = $url;
         return $this;
     }
 
     /**
      * Get the callback URL to be used by Hub Servers when communicating with
      * this Subscriber
      *
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return string
      */
     public function getCallbackUrl()
     {
         if (empty($this->_callbackUrl)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('A valid Callback URL MUST be'
                 . ' set before attempting any operation');
         }
         return $this->_callbackUrl;
     }
 
     /**
      * Set preferred verification mode (sync or async). By default, this
      * Subscriber prefers synchronous verification, but does support
      * asynchronous if that's the Hub Server's utilised mode.
      *
      * Zend_Feed_Pubsubhubbub_Subscriber will always send both modes, whose
      * order of occurance in the parameter list determines this preference.
      *
      * @param  string $mode Should be 'sync' or 'async'
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setPreferredVerificationMode($mode)
     {
         if ($mode !== Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC
         && $mode !== Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_ASYNC) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid preferred'
                 . ' mode specified: "' . $mode . '" but should be one of'
                 . ' Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC or'
                 . ' Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_ASYNC');
         }
         $this->_preferredVerificationMode = $mode;
         return $this;
     }
 
     /**
      * Get preferred verification mode (sync or async).
      *
      * @return string
      */
     public function getPreferredVerificationMode()
     {
         return $this->_preferredVerificationMode;
     }
 
     /**
      * Add a Hub Server URL supported by Publisher
      *
      * @param  string $url
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function addHubUrl($url)
     {
         if (empty($url) || !is_string($url) || !Zend_Uri::check($url)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "url"'
                 . ' of "' . $url . '" must be a non-empty string and a valid'
                 . ' URL');
         }
         $this->_hubUrls[] = $url;
         return $this;
     }
 
     /**
      * Add an array of Hub Server URLs supported by Publisher
      *
      * @param  array $urls
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function addHubUrls(array $urls)
     {
         foreach ($urls as $url) {
             $this->addHubUrl($url);
         }
         return $this;
     }
 
     /**
      * Remove a Hub Server URL
      *
      * @param  string $url
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function removeHubUrl($url)
     {
         if (!in_array($url, $this->getHubUrls())) {
             return $this;
         }
         $key = array_search($url, $this->_hubUrls);
         unset($this->_hubUrls[$key]);
         return $this;
     }
 
     /**
      * Return an array of unique Hub Server URLs currently available
      *
      * @return array
      */
     public function getHubUrls()
     {
         $this->_hubUrls = array_unique($this->_hubUrls);
         return $this->_hubUrls;
     }
 
     /**
      * Add authentication credentials for a given URL
      *
      * @param  string $url
      * @param  array  $authentication
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function addAuthentication($url, array $authentication)
     {
         if (empty($url) || !is_string($url) || !Zend_Uri::check($url)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "url"'
                 . ' of "' . $url . '" must be a non-empty string and a valid'
                 . ' URL');
         }
         $this->_authentications[$url] = $authentication;
         return $this;
     }
 
     /**
      * Add authentication credentials for hub URLs
      *
      * @param  array $authentications
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function addAuthentications(array $authentications)
     {
         foreach ($authentications as $url => $authentication) {
             $this->addAuthentication($url, $authentication);
         }
         return $this;
     }
 
     /**
      * Get all hub URL authentication credentials
      *
      * @return array
      */
     public function getAuthentications()
     {
         return $this->_authentications;
     }
 
     /**
      * Set flag indicating whether or not to use a path parameter
      *
      * @param  bool $bool
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function usePathParameter($bool = true)
     {
         $this->_usePathParameter = $bool;
         return $this;
     }
 
     /**
      * Add an optional parameter to the (un)subscribe requests
      *
      * @param  string      $name
      * @param  string|null $value
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setParameter($name, $value = null)
     {
         if (is_array($name)) {
             $this->setParameters($name);
             return $this;
         }
         if (empty($name) || !is_string($name)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "name"'
                 . ' of "' . $name . '" must be a non-empty string');
         }
         if ($value === null) {
             $this->removeParameter($name);
             return $this;
         }
         if (empty($value) || (!is_string($value) && $value !== null)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "value"'
                 . ' of "' . $value . '" must be a non-empty string');
         }
         $this->_parameters[$name] = $value;
         return $this;
     }
 
     /**
      * Add an optional parameter to the (un)subscribe requests
      *
      * @param  array $parameters
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setParameters(array $parameters)
     {
         foreach ($parameters as $name => $value) {
             $this->setParameter($name, $value);
         }
         return $this;
     }
 
     /**
      * Remove an optional parameter for the (un)subscribe requests
      *
      * @param  string $name
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function removeParameter($name)
     {
         if (empty($name) || !is_string($name)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid parameter "name"'
                 . ' of "' . $name . '" must be a non-empty string');
         }
         if (array_key_exists($name, $this->_parameters)) {
             unset($this->_parameters[$name]);
         }
         return $this;
     }
 
     /**
      * Return an array of optional parameters for (un)subscribe requests
      *
      * @return array
      */
     public function getParameters()
     {
         return $this->_parameters;
     }
 
     /**
      * Sets an instance of Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface used to background
      * save any verification tokens associated with a subscription or other.
      *
      * @param  Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface $storage
      * @return Zend_Feed_Pubsubhubbub_Subscriber
      */
     public function setStorage(Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface $storage)
     {
         $this->_storage = $storage;
         return $this;
     }
 
     /**
      * Gets an instance of Zend_Feed_Pubsubhubbub_Storage_StorageInterface used
      * to background save any verification tokens associated with a subscription
      * or other.
      *
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface
      */
     public function getStorage()
     {
         if ($this->_storage === null) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('No storage vehicle '
                 . 'has been set.');
         }
         return $this->_storage;
     }
 
     /**
      * Subscribe to one or more Hub Servers using the stored Hub URLs
      * for the given Topic URL (RSS or Atom feed)
      */
     public function subscribeAll()
     {
         return $this->_doRequest('subscribe');
     }
 
     /**
      * Unsubscribe from one or more Hub Servers using the stored Hub URLs
      * for the given Topic URL (RSS or Atom feed)
      */
     public function unsubscribeAll()
     {
         return $this->_doRequest('unsubscribe');
     }
 
     /**
      * Returns a boolean indicator of whether the notifications to Hub
      * Servers were ALL successful. If even one failed, FALSE is returned.
      *
      * @return bool
      */
     public function isSuccess()
     {
         if (count($this->_errors) > 0) {
             return false;
         }
         return true;
     }
 
     /**
      * Return an array of errors met from any failures, including keys:
      * 'response' => the Zend_Http_Response object from the failure
      * 'hubUrl' => the URL of the Hub Server whose notification failed
      *
      * @return array
      */
     public function getErrors()
     {
         return $this->_errors;
     }
 
     /**
      * Return an array of Hub Server URLs who returned a response indicating
      * operation in Asynchronous Verification Mode, i.e. they will not confirm
      * any (un)subscription immediately but at a later time (Hubs may be
      * doing this as a batch process when load balancing)
      *
      * @return array
      */
     public function getAsyncHubs()
     {
         return $this->_asyncHubs;
     }
 
     /**
      * Executes an (un)subscribe request
      *
      * @param  string $mode
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @throws Zend_Http_Client_Exception
      */
     protected function _doRequest($mode)
     {
         $client = $this->_getHttpClient();
         $hubs   = $this->getHubUrls();
         if (empty($hubs)) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('No Hub Server URLs'
                 . ' have been set so no subscriptions can be attempted');
         }
         $this->_errors = array();
         $this->_asyncHubs = array();
         foreach ($hubs as $url) {
             if (array_key_exists($url, $this->_authentications)) {
                 $auth = $this->_authentications[$url];
                 $client->setAuth($auth[0], $auth[1]);
             }
             $client->setUri($url);
             $client->setRawData(
                 $this->_getRequestParameters($url, $mode),
                 'application/x-www-form-urlencoded'
             );
             $response = $client->request();
             if ($response->getStatus() !== 204
                 && $response->getStatus() !== 202
             ) {
                 $this->_errors[] = array(
                     'response' => $response,
                     'hubUrl'   => $url,
                 );
             /**
              * At first I thought it was needed, but the backend storage will
              * allow tracking async without any user interference. It's left
              * here in case the user is interested in knowing what Hubs
              * are using async verification modes so they may update Models and
              * move these to asynchronous processes.
              */
             } elseif ($response->getStatus() == 202) {
                 $this->_asyncHubs[] = array(
                     'response' => $response,
                     'hubUrl'   => $url,
                 );
             }
         }
     }
 
     /**
      * Get a basic prepared HTTP client for use
      *
      * @return Zend_Http_Client
      */
     protected function _getHttpClient()
     {
         $client = Zend_Feed_Pubsubhubbub::getHttpClient();
         $client->setMethod(Zend_Http_Client::POST);
         $client->setConfig(array('useragent' => 'Zend_Feed_Pubsubhubbub_Subscriber/'
             . Zend_Version::VERSION));
         return $client;
     }
 
     /**
      * Return a list of standard protocol/optional parameters for addition to
      * client's POST body that are specific to the current Hub Server URL
      *
      * @param  string $hubUrl
      * @param  string $mode
      * @throws Zend_Feed_Pubsubhubbub_Exception
      * @return string
      */
     protected function _getRequestParameters($hubUrl, $mode)
     {
         if (!in_array($mode, array('subscribe', 'unsubscribe'))) {
             // require_once 'Zend/Feed/Pubsubhubbub/Exception.php';
             throw new Zend_Feed_Pubsubhubbub_Exception('Invalid mode specified: "'
                 . $mode . '" which should have been "subscribe" or "unsubscribe"');
         }
 
         $params = array(
             'hub.mode'  => $mode,
             'hub.topic' => $this->getTopicUrl(),
         );
 
         if ($this->getPreferredVerificationMode()
                 == Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC
         ) {
             $vmodes = array(
                 Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC,
                 Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_ASYNC,
             );
         } else {
             $vmodes = array(
                 Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_ASYNC,
                 Zend_Feed_Pubsubhubbub::VERIFICATION_MODE_SYNC,
             );
         }
         $params['hub.verify'] = array();
         foreach($vmodes as $vmode) {
             $params['hub.verify'][] = $vmode;
         }
 
         /**
          * Establish a persistent verify_token and attach key to callback
          * URL's path/querystring
          */
         $key   = $this->_generateSubscriptionKey($params, $hubUrl);
         $token = $this->_generateVerifyToken();
         $params['hub.verify_token'] = $token;
 
         // Note: query string only usable with PuSH 0.2 Hubs
         if (!$this->_usePathParameter) {
             $params['hub.callback'] = $this->getCallbackUrl()
                 . '?xhub.subscription=' . Zend_Feed_Pubsubhubbub::urlencode($key);
         } else {
             $params['hub.callback'] = rtrim($this->getCallbackUrl(), '/')
                 . '/' . Zend_Feed_Pubsubhubbub::urlencode($key);
         }
         if ($mode == 'subscribe' && $this->getLeaseSeconds() !== null) {
             $params['hub.lease_seconds'] = $this->getLeaseSeconds();
         }
 
         // hub.secret not currently supported
         $optParams = $this->getParameters();
         foreach ($optParams as $name => $value) {
             $params[$name] = $value;
         }
 
         // store subscription to storage
         $now = new Zend_Date;
         $expires = null;
         if (isset($params['hub.lease_seconds'])) {
             $expires = $now->add($params['hub.lease_seconds'], Zend_Date::SECOND)
                 ->get('yyyy-MM-dd HH:mm:ss');
         }
         $data = array(
             'id'                 => $key,
             'topic_url'          => $params['hub.topic'],
             'hub_url'            => $hubUrl,
             'created_time'       => $now->get('yyyy-MM-dd HH:mm:ss'),
             'lease_seconds'      => $expires,
             'verify_token'       => hash('sha256', $params['hub.verify_token']),
             'secret'             => null,
             'expiration_time'    => $expires,
             'subscription_state' => Zend_Feed_Pubsubhubbub::SUBSCRIPTION_NOTVERIFIED,
         );
         $this->getStorage()->setSubscription($data);
 
         return $this->_toByteValueOrderedString(
             $this->_urlEncode($params)
         );
     }
 
     /**
      * Simple helper to generate a verification token used in (un)subscribe
      * requests to a Hub Server. Follows no particular method, which means
      * it might be improved/changed in future.
      *
      * @return string
      */
     protected function _generateVerifyToken()
     {
         if (!empty($this->_testStaticToken)) {
             return $this->_testStaticToken;
         }
         return uniqid(rand(), true) . time();
     }
 
     /**
      * Simple helper to generate a verification token used in (un)subscribe
      * requests to a Hub Server.
      *
      * @param  array  $params
      * @param  string $hubUrl The Hub Server URL for which this token will apply
      * @return string
      */
     protected function _generateSubscriptionKey(array $params, $hubUrl)
     {
         $keyBase = $params['hub.topic'] . $hubUrl;
         $key     = md5($keyBase);
         return $key;
     }
 
     /**
      * URL Encode an array of parameters
      *
      * @param  array $params
      * @return array
      */
     protected function _urlEncode(array $params)
     {
         $encoded = array();
         foreach ($params as $key => $value) {
             if (is_array($value)) {
                 $ekey = Zend_Feed_Pubsubhubbub::urlencode($key);
                 $encoded[$ekey] = array();
                 foreach ($value as $duplicateKey) {
                     $encoded[$ekey][]
                         = Zend_Feed_Pubsubhubbub::urlencode($duplicateKey);
                 }
             } else {
                 $encoded[Zend_Feed_Pubsubhubbub::urlencode($key)]
                     = Zend_Feed_Pubsubhubbub::urlencode($value);
             }
         }
         return $encoded;
     }
 
     /**
      * Order outgoing parameters
      *
      * @param  array $params
      * @return array
      */
     protected function _toByteValueOrderedString(array $params)
     {
         $return = array();
         uksort($params, 'strnatcmp');
         foreach ($params as $key => $value) {
             if (is_array($value)) {
                 foreach ($value as $keyduplicate) {
                     $return[] = $key . '=' . $keyduplicate;
                 }
             } else {
                 $return[] = $key . '=' . $value;
             }
         }
         return implode('&', $return);
     }
 
     /**
      * This is STRICTLY for testing purposes only...
      */
     protected $_testStaticToken = null;
 
     final public function setTestStaticToken($token)
     {
         $this->_testStaticToken = (string) $token;
     }
 }