common.inc

<?php
// $Id$

/**
 * @file
 * Common functions that many Drupal modules will need to reference.
 *
 * The functions that are critical and need to be available even when serving
 * a cached page are instead located in bootstrap.inc.
 */

/**
 * Return status for saving which involved creating a new item.
 */
define('SAVED_NEW', 1);

/**
 * Return status for saving which involved an update to an existing item.
 */
define('SAVED_UPDATED', 2);

/**
 * Return status for saving which deleted an existing item.
 */
define('SAVED_DELETED', 3);

/**
 * Set content for a specified region.
 *
 * @param $region
 *   Page region the content is assigned to.
 *
 * @param $data
 *   Content to be set.
 */
function drupal_set_content($region = NULL, $data = NULL) {
  static $content = array();

  if (!is_null($region) && !is_null($data)) {
    $content[$region][] = $data;
  }
  return $content;
}

/**
 * Get assigned content.
 *
 * @param $region
 *   A specified region to fetch content for. If NULL, all regions will be returned.
 *
 * @param $delimiter
 *   Content to be inserted between exploded array elements.
 */
function drupal_get_content($region = NULL, $delimiter = ' ') {
  $content = drupal_set_content();
  if (isset($region)) {
    if (isset($content[$region]) && is_array($content[$region])) {
      return implode($delimiter, $content[$region]);
    }
  }
  else {
    foreach (array_keys($content) as $region) {
      if (is_array($content[$region])) {
        $content[$region] = implode($delimiter, $content[$region]);
      }
    }
    return $content;
  }
}

/**
 * Set the breadcrumb trail for the current page.
 *
 * @param $breadcrumb
 *   Array of links, starting with "home" and proceeding up to but not including
 *   the current page.
 */
function drupal_set_breadcrumb($breadcrumb = NULL) {
  static $stored_breadcrumb;

  if (!is_null($breadcrumb)) {
    $stored_breadcrumb = $breadcrumb;
  }
  return $stored_breadcrumb;
}

/**
 * Get the breadcrumb trail for the current page.
 */
function drupal_get_breadcrumb() {
  $breadcrumb = drupal_set_breadcrumb();

  if (is_null($breadcrumb)) {
    $breadcrumb = menu_get_active_breadcrumb();
  }

  return $breadcrumb;
}

/**
 * Add output to the head tag of the HTML page.
 * This function can be called as long the headers aren't sent.
 */
function drupal_set_html_head($data = NULL) {
  static $stored_head = '';

  if (!is_null($data)) {
    $stored_head .= $data ."\n";
  }
  return $stored_head;
}

/**
 * Retrieve output to be displayed in the head tag of the HTML page.
 */
function drupal_get_html_head() {
  $output = "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />\n";
  return $output . drupal_set_html_head();
}

/**
 * Reset the static variable which holds the aliases mapped for this request.
 */
function drupal_clear_path_cache() {
  drupal_lookup_path('wipe');
}

/**
 * Set an HTTP response header for the current page.
 */
function drupal_set_header($header = NULL) {
  // We use an array to guarantee there are no leading or trailing delimiters.
  // Otherwise, header('') could get called when serving the page later, which
  // ends HTTP headers prematurely on some PHP versions.
  static $stored_headers = array();

  if (strlen($header)) {
    header($header);
    $stored_headers[] = $header;
  }
  return implode("\n", $stored_headers);
}

/**
 * Get the HTTP response headers for the current page.
 */
function drupal_get_headers() {
  return drupal_set_header();
}

/*
 * Add a feed URL for the current page.
 *
 * @param $url
 *   The url for the feed
 * @param $title
 *   The title of the feed
 */
function drupal_add_feed($url = NULL, $title = '') {
  static $stored_feed_links = array();

  if (!is_null($url)) {
    $stored_feed_links[$url] = theme('feed_icon', $url);

    drupal_add_link(array('rel' => 'alternate',
                          'type' => 'application/rss+xml',
                          'title' => $title,
                          'href' => $url));
  }
  return $stored_feed_links;
}

/**
 * Get the feed URLs for the current page.
 *
 * @param $delimiter
 *   The delimiter to split feeds by
 */
function drupal_get_feeds($delimiter = "\n") {
  $feeds = drupal_add_feed();
  return implode($feeds, $delimiter);
}

/**
 * @name HTTP handling
 * @{
 * Functions to properly handle HTTP responses.
 */

/**
 * Parse an array into a valid urlencoded query string.
 *
 * @param $query
 *   The array to be processed e.g. $_GET
 * @param $exclude
 *   The array filled with keys to be excluded. Use parent[child] to exclude nested items.
 * @param $urlencode
 *   If TRUE, the keys and values are both urlencoded.
 * @param $parent
 *   Should not be passed, only used in recursive calls
 * @return
 *   urlencoded string which can be appended to/as the URL query string
 */
function drupal_query_string_encode($query, $exclude = array(), $parent = '') {
  $params = array();

  foreach ($query as $key => $value) {
    $key = drupal_urlencode($key);
    if ($parent) {
      $key = $parent .'['. $key .']';
    }

    if (in_array($key, $exclude)) {
      continue;
    }

    if (is_array($value)) {
      $params[] = drupal_query_string_encode($value, $exclude, $key);
    }
    else {
      $params[] = $key .'='. drupal_urlencode($value);
    }
  }

  return implode('&', $params);
}

/**
 * Prepare a destination query string for use in combination with
 * drupal_goto(). Used to direct the user back to the referring page
 * after completing a form. By default the current URL is returned.
 * If a destination exists in the previous request, that destination
 * is returned. As such, a destination can persist across multiple
 * pages.
 *
 * @see drupal_goto()
 */
function drupal_get_destination() {
  if (isset($_REQUEST['destination'])) {
    return 'destination='. urlencode($_REQUEST['destination']);
  }
  else {
    // Use $_REQUEST here to retrieve the original path.
    $path = isset($_REQUEST['q']) ? drupal_get_path_alias($_REQUEST['q']) : '';
    $query = drupal_query_string_encode($_GET, array('q'));
    if ($query != '') {
      $path .= '?'. $query;
    }
    return 'destination='. urlencode($path);
  }
}

/**
 * Send the user to a different Drupal page.
 *
 * This issues an on-site HTTP redirect. The function makes sure the redirected
 * URL is formatted correctly.
 *
 * Usually the redirected URL is constructed from this function's input
 * parameters. However you may override that behavior by setting a
 * <em>destination</em> in either the $_REQUEST-array (i.e. by using
 * the query string of an URI) or the $_REQUEST['edit']-array (i.e. by
 * using a hidden form field). This is used to direct the user back to
 * the proper page after completing a form. For example, after editing
 * a post on the 'admin/content/node'-page or after having logged on using the
 * 'user login'-block in a sidebar. The function drupal_get_destination()
 * can be used to help set the destination URL.
 *
 * It is advised to use drupal_goto() instead of PHP's header(), because
 * drupal_goto() will append the user's session ID to the URI when PHP is
 * compiled with "--enable-trans-sid".
 *
 * This function ends the request; use it rather than a print theme('page')
 * statement in your menu callback.
 *
 * @param $path
 *   A Drupal path or a full URL.
 * @param $query
 *   The query string component, if any.
 * @param $fragment
 *   The destination fragment identifier (named anchor).
 *
 * @see drupal_get_destination()
 */
function drupal_goto($path = '', $query = NULL, $fragment = NULL) {
  if (isset($_REQUEST['destination'])) {
    extract(parse_url($_REQUEST['destination']));
  }
  else if (isset($_REQUEST['edit']['destination'])) {
    extract(parse_url($_REQUEST['edit']['destination']));
  }

  $url = url($path, $query, $fragment, TRUE);

  // Before the redirect, allow modules to react to the end of the page request.
  module_invoke_all('exit', $url);

  header('Location: '. $url);

  // The "Location" header sends a REDIRECT status code to the http
  // daemon. In some cases this can go wrong, so we make sure none
  // of the code below the drupal_goto() call gets executed when we redirect.
  exit();
}

/**
 * Generates a site off-line message
 */
function drupal_site_offline() {
  drupal_set_header('HTTP/1.0 503 Service unavailable');
  drupal_set_title(t('Site off-line'));
  print theme('maintenance_page', filter_xss_admin(variable_get('site_offline_message',
    t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => variable_get('site_name', t('This Drupal site')))))));
}

/**
 * Generates a 404 error if the request can not be handled.
 */
function drupal_not_found() {
  drupal_set_header('HTTP/1.0 404 Not Found');
  watchdog('page not found', check_plain($_GET['q']), WATCHDOG_WARNING);

  $return = '';

  if (variable_get('site_404_message_display', TRUE)) {
    $message = variable_get('site_404_message', t('We are sorry, the requested page was not found on this webserver. Either the URL does not exist or the page you were looking has been deleted.'));
    drupal_set_message(filter_xss_admin($message));
  }

  // Keep old path for reference
  if (!isset($_REQUEST['destination'])) {
    $_REQUEST['destination'] = $_GET['q'];
  }

  $path = drupal_get_normal_path(variable_get('site_404', ''));
  if (!empty($path) && $path != $_GET['q']) {
    menu_set_active_item($path);
    $return = menu_execute_active_handler();
  }
  else {
    // Redirect to a non-existent menu item to make possible tabs disappear.
    menu_set_active_item('');
  }

  if (empty($return) || $return == MENU_NOT_FOUND || $return == MENU_ACCESS_DENIED) {
    drupal_set_title(t('404 - File not found'));
    $return = '&nbsp;';
  }
  // To conserve CPU and bandwidth, omit the blocks
  print theme('page', $return, FALSE);
}

/**
 * Generates a 403 error if the request is not allowed.
 */
function drupal_access_denied() {
  drupal_set_header('HTTP/1.0 403 Forbidden');
  watchdog('access denied', check_plain($_GET['q']), WATCHDOG_WARNING);

  $return = '';

  if (variable_get('site_403_message_display', TRUE)) {
    $message = variable_get('site_403_message', t('We are sorry, you do not have access to this page. If you are not already logged in, please try to login and then visit this page again. If you think should be able to access this page, please contact site admins.'));
    drupal_set_message(filter_xss_admin($message));
  }

  // Keep old path for reference
  if (!isset($_REQUEST['destination'])) {
    $_REQUEST['destination'] = $_GET['q'];
  }

  $path = drupal_get_normal_path(variable_get('site_403', ''));
  if (!empty($path) && $path != $_GET['q']) {
    menu_set_active_item($path);
    $return = menu_execute_active_handler();
  }
  else {
    // Redirect to a non-existent menu item to make possible tabs disappear.
    menu_set_active_item('');
  }

  if (empty($return) || $return == MENU_NOT_FOUND || $return == MENU_ACCESS_DENIED) {
    drupal_set_title(t('403 - Access denied'));
    $return = '&nbsp;';
  }
  print theme('page', $return);
}

/**
 * Perform an HTTP request.
 *
 * This is a flexible and powerful HTTP client implementation. Correctly handles
 * GET, POST, PUT or any other HTTP requests. Handles redirects.
 *
 * @param $url
 *   A string containing a fully qualified URI.
 * @param $headers
 *   An array containing an HTTP header => value pair.
 * @param $method
 *   A string defining the HTTP request to use.
 * @param $data
 *   A string containing data to include in the request.
 * @param $retry
 *   An integer representing how many times to retry the request in case of a
 *   redirect.
 * @return
 *   An object containing the HTTP request headers, response code, headers,
 *   data, and redirect status.
 */
function drupal_http_request($url, $headers = array(), $method = 'GET', $data = NULL, $retry = 3) {
  $result = new StdClass();

  // Parse the URL, and make sure we can handle the schema.
  $uri = parse_url($url);
  switch ($uri['scheme']) {
    case 'http':
      $port = isset($uri['port']) ? $uri['port'] : 80;
      $host = $uri['host'] . ($port != 80 ? ':'. $port : '');
      $fp = @fsockopen($uri['host'], $port, $errno, $errstr, 15);
      break;
    case 'https':
      // Note: Only works for PHP 4.3 compiled with OpenSSL.
      $port = isset($uri['port']) ? $uri['port'] : 443;
      $host = $uri['host'] . ($port != 443 ? ':'. $port : '');
      $fp = @fsockopen('ssl://'. $uri['host'], $port, $errno, $errstr, 20);
      break;
    default:
      $result->error = 'invalid schema '. $uri['scheme'];
      return $result;
  }

  // Make sure the socket opened properly.
  if (!$fp) {
    $result->error = trim($errno .' '. $errstr);
    return $result;
  }

  // Construct the path to act on.
  $path = isset($uri['path']) ? $uri['path'] : '/';
  if (isset($uri['query'])) {
    $path .= '?'. $uri['query'];
  }

  // Create HTTP request.
  $defaults = array(
    // RFC 2616: "non-standard ports MUST, default ports MAY be included".
    // We don't add the port to prevent from breaking rewrite rules checking
    // the host that do not take into account the port number.
    'Host' => "Host: $host",
    'User-Agent' => 'User-Agent: Drupal (+http://drupal.org/)',
    'Content-Length' => 'Content-Length: '. strlen($data)
  );

  foreach ($headers as $header => $value) {
    $defaults[$header] = $header .': '. $value;
  }

  $request = $method .' '. $path ." HTTP/1.0\r\n";
  $request .= implode("\r\n", $defaults);
  $request .= "\r\n\r\n";
  if ($data) {
    $request .= $data ."\r\n";
  }
  $result->request = $request;

  fwrite($fp, $request);

  // Fetch response.
  $response = '';
  while (!feof($fp) && $chunk = fread($fp, 1024)) {
    $response .= $chunk;
  }
  fclose($fp);

  // Parse response.
  list($split, $result->data) = explode("\r\n\r\n", $response, 2);
  $split = preg_split("/\r\n|\n|\r/", $split);

  list($protocol, $code, $text) = explode(' ', trim(array_shift($split)), 3);
  $result->headers = array();

  // Parse headers.
  while ($line = trim(array_shift($split))) {
    list($header, $value) = explode(':', $line, 2);
    if (isset($result->headers[$header]) && $header == 'Set-Cookie') {
      // RFC 2109: the Set-Cookie response header comprises the token Set-
      // Cookie:, followed by a comma-separated list of one or more cookies.
      $result->headers[$header] .= ','. trim($value);
    }
    else {
      $result->headers[$header] = trim($value);
    }
  }

  $responses = array(
    100 => 'Continue', 101 => 'Switching Protocols',
    200 => 'OK', 201 => 'Created', 202 => 'Accepted', 203 => 'Non-Authoritative Information', 204 => 'No Content', 205 => 'Reset Content', 206 => 'Partial Content',
    300 => 'Multiple Choices', 301 => 'Moved Permanently', 302 => 'Found', 303 => 'See Other', 304 => 'Not Modified', 305 => 'Use Proxy', 307 => 'Temporary Redirect',
    400 => 'Bad Request', 401 => 'Unauthorized', 402 => 'Payment Required', 403 => 'Forbidden', 404 => 'Not Found', 405 => 'Method Not Allowed', 406 => 'Not Acceptable', 407 => 'Proxy Authentication Required', 408 => 'Request Time-out', 409 => 'Conflict', 410 => 'Gone', 411 => 'Length Required', 412 => 'Precondition Failed', 413 => 'Request Entity Too Large', 414 => 'Request-URI Too Large', 415 => 'Unsupported Media Type', 416 => 'Requested range not satisfiable', 417 => 'Expectation Failed',
    500 => 'Internal Server Error', 501 => 'Not Implemented', 502 => 'Bad Gateway', 503 => 'Service Unavailable', 504 => 'Gateway Time-out', 505 => 'HTTP Version not supported'
  );
  // RFC 2616 states that all unknown HTTP codes must be treated the same as
  // the base code in their class.
  if (!isset($responses[$code])) {
    $code = floor($code / 100) * 100;
  }

  switch ($code) {
    case 200: // OK
    case 304: // Not modified
      break;
    case 301: // Moved permanently
    case 302: // Moved temporarily
    case 307: // Moved temporarily
      $location = $result->headers['Location'];

      if ($retry) {
        $result = drupal_http_request($result->headers['Location'], $headers, $method, $data, --$retry);
        $result->redirect_code = $result->code;
      }
      $result->redirect_url = $location;

      break;
    default:
      $result->error = $text;
  }

  $result->code = $code;
  return $result;
}
/**
 * @} End of "HTTP handling".
 */

/**
 * Log errors as defined by administrator
 * Error levels:
 *  0 = Log errors to database.
 *  1 = Log errors to database and to screen.
 */
function error_handler($errno, $message, $filename, $line) {
  // If the @ error suppression operator was used, error_reporting is temporarily set to 0
  if (error_reporting() == 0) {
    return;
  }

  if ($errno & (E_ALL ^ E_NOTICE)) {
    $types = array(1 => 'error', 2 => 'warning', 4 => 'parse error', 8 => 'notice', 16 => 'core error', 32 => 'core warning', 64 => 'compile error', 128 => 'compile warning', 256 => 'user error', 512 => 'user warning', 1024 => 'user notice', 2048 => 'strict warning');
    $entry = $types[$errno] .': '. $message .' in '. $filename .' on line '. $line .'.';

    // Force display of error messages in update.php
    if (variable_get('error_level', 1) == 1 || strstr($_SERVER['PHP_SELF'], 'update.php')) {
      drupal_set_message($entry, 'error');
    }

    watchdog('php', t('%message in %file on line %line.', array('%error' => $types[$errno], '%message' => $message, '%file' => $filename, '%line' => $line)), WATCHDOG_ERROR);
  }
}

function _fix_gpc_magic(&$item) {
  if (is_array($item)) {
    array_walk($item, '_fix_gpc_magic');
  }
  else {
    $item = stripslashes($item);
  }
}

/**
 * Correct double-escaping problems caused by "magic quotes" in some PHP
 * installations.
 */
function fix_gpc_magic() {
  static $fixed = FALSE;
  if (!$fixed && ini_get('magic_quotes_gpc')) {
    array_walk($_GET, '_fix_gpc_magic');
    array_walk($_POST, '_fix_gpc_magic');
    array_walk($_COOKIE, '_fix_gpc_magic');
    array_walk($_REQUEST, '_fix_gpc_magic');
    $fixed = TRUE;
  }
}

/**
 * Initialize the localization system.
 */
function locale_initialize() {
  global $user;

  if (function_exists('i18n_get_lang')) {
    return i18n_get_lang();
  }

  if (function_exists('locale')) {
    $languages = locale_supported_languages();
    $languages = $languages['name'];
  }
  else {
    // Ensure the locale/language is correctly returned, even without locale.module.
    // Useful for e.g. XML/HTML 'lang' attributes.
    $languages = array('en' => 'English');
  }
  if ($user->uid && isset($languages[$user->language])) {
    return $user->language;
  }
  else {
    return key($languages);
  }
}

/**
 * Translate strings to the current locale.
 *
 * When using t(), try to put entire sentences and strings in one t() call.
 * This makes it easier for translators. HTML markup within translation strings
 * is acceptable, if necessary. The suggested syntax for a link embedded
 * within a translation string is:
 * @code
 *   $msg = t('You must log in below or <a href="@url">create a new
 *             account</a> before viewing the next page.', array('@url'
 *             => url('user/register')));
 * @endcode
 * We suggest the same syntax for links to other sites. This makes it easy to
 * change link URLs if needed (which happens often) without requiring updates
 * to translations.
 *
 * @param $string
 *   A string containing the English string to translate.
 * @param $args
 *   An associative array of replacements to make after translation. Incidences
 *   of any key in this array are replaced with the corresponding value.
 *   Based on the first character of the key, the value is escaped and/or themed:
 *    - !variable: inserted as is
 *    - @variable: escape plain text to HTML (check_plain)
 *    - %variable: escape text and theme as a placeholder for user-submitted
 *      content (check_plain + theme_placeholder)
 * @return
 *   The translated string.
 */
function t($string, $args = 0) {
  global $locale;
  if (function_exists('locale') && $locale != 'en') {
    $string = locale($string);
  }
  if (!$args) {
    return $string;
  }
  else {
    // Transform arguments before inserting them
    array_walk($args, '_t');
    return strtr($string, $args);
  }
}

/**
 * Helper function: apply the appropriate transformation to st() and t()
 * placeholders.
 */
function _t(&$value, $key) {
  switch ($key[0]) {
    // Escaped only
    case '@':
      $value = check_plain($value);
      return;
    // Escaped and placeholder
    case '%':
    default:
      $value = theme('placeholder', $value);
      return;
    // Pass-through
    case '!':
  }
}

/**
 * @defgroup validation Input validation
 * @{
 * Functions to validate user input.
 */

/**
 * Verify the syntax of the given e-mail address.
 *
 * Empty e-mail addresses are allowed. See RFC 2822 for details.
 *
 * @param $mail
 *   A string containing an e-mail address.
 * @return
 *   TRUE if the address is in a valid format.
 */
function valid_email_address($mail) {
  $user = '[a-zA-Z0-9_\-\.\+\^!#\$%&*+\/\=\?\`\|\{\}~\']+';
  $domain = '(?:(?:[a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.?)+';
  $ipv4 = '[0-9]{1,3}(\.[0-9]{1,3}){3}';
  $ipv6 = '[0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7}';

  return preg_match("/^$user@($domain|(\[($ipv4|$ipv6)\]))$/", $mail);
}

/**
 * Verify the syntax of the given URL.
 *
 * @param $url
 *   The URL to verify.
 * @param $absolute
 *   Whether the URL is absolute (beginning with a scheme such as "http:").
 * @return
 *   TRUE if the URL is in a valid format.
 */
function valid_url($url, $absolute = FALSE) {
  $allowed_characters = '[a-z0-9\/:_\-_\.\?\$,~=#&%\+]';
  if ($absolute) {
    return preg_match("/^(http|https|ftp):\/\/". $allowed_characters ."+$/i", $url);
  }
  else {
    return preg_match("/^". $allowed_characters ."+$/i", $url);
  }
}

/**
 * Register an event for the current visitor (hostname/IP) to the flood control mechanism.
 *
 * @param $name
 *   The name of the event.
 */
function flood_register_event($name) {
  db_query("INSERT INTO {flood} (event, hostname, timestamp) VALUES ('%s', '%s', %d)", $name, $_SERVER['REMOTE_ADDR'], time());
}

/**
 * Check if the current visitor (hostname/IP) is allowed to proceed with the specified event.
 * The user is allowed to proceed if he did not trigger the specified event more than
 * $threshold times per hour.
 *
 * @param $name
 *   The name of the event.
 * @param $number
 *   The maximum number of the specified event per hour (per visitor).
 * @return
 *   True if the user did not exceed the hourly threshold. False otherwise.
 */
function flood_is_allowed($name, $threshold) {
  $number = db_num_rows(db_query("SELECT event FROM {flood} WHERE event = '%s' AND hostname = '%s' AND timestamp > %d", $name, $_SERVER['REMOTE_ADDR'], time() - 3600));
  return ($number < $threshold ? TRUE : FALSE);
}

function check_file($filename) {
  return is_uploaded_file($filename);
}

/**
 * Prepare a URL for use in an HTML attribute. Strips harmful protocols.
 *
 */
function check_url($uri) {
  return filter_xss_bad_protocol($uri, FALSE);
}

/**
 * @defgroup format Formatting
 * @{
 * Functions to format numbers, strings, dates, etc.
 */

/**
 * Formats an RSS channel.
 *
 * Arbitrary elements may be added using the $args associative array.
 */
function format_rss_channel($title, $link, $description, $items, $language = 'en', $args = array()) {
  // arbitrary elements may be added using the $args associative array

  $output = "<channel>\n";
  $output .= ' <title>'. check_plain($title) ."</title>\n";
  $output .= ' <link>'. check_url($link) ."</link>\n";

  // The RSS 2.0 "spec" doesn't indicate HTML can be used in the description.
  // We strip all HTML tags, but need to prevent double encoding from properly
  // escaped source data (such as &amp becoming &amp;amp;).
  $output .= ' <description>'. check_plain(decode_entities(strip_tags($description))) ."</description>\n";
  $output .= ' <language>'. check_plain($language) ."</language>\n";
  $output .= format_xml_elements($args);
  $output .= $items;
  $output .= "</channel>\n";

  return $output;
}

/**
 * Format a single RSS item.
 *
 * Arbitrary elements may be added using the $args associative array.
 */
function format_rss_item($title, $link, $description, $args = array()) {
  $output = "<item>\n";
  $output .= ' <title>'. check_plain($title) ."</title>\n";
  $output .= ' <link>'. check_url($link) ."</link>\n";
  $output .= ' <description>'. check_plain($description) ."</description>\n";
  $output .= format_xml_elements($args);
  $output .= "</item>\n";

  return $output;
}

/**
 * Format XML elements.
 *
 * @param $array
 *   An array where each item represent an element and is either a:
 *   - (key => value) pair (<key>value</key>)
 *   - Associative array with fields:
 *     - 'key': element name
 *     - 'value': element contents
 *     - 'attributes': associative array of element attributes
 *
 * In both cases, 'value' can be a simple string, or it can be another array
 * with the same format as $array itself for nesting.
 */
function format_xml_elements($array) {
  foreach ($array as $key => $value) {
    if (is_numeric($key)) {
      if ($value['key']) {
        $output .= ' <'. $value['key'];
        if (isset($value['attributes']) && is_array($value['attributes'])) {
          $output .= drupal_attributes($value['attributes']);
        }

        if ($value['value'] != '') {
          $output .= '>'. (is_array($value['value']) ? format_xml_elements($value['value']) : check_plain($value['value'])) .'</'. $value['key'] .">\n";
        }
        else {
          $output .= " />\n";
        }
      }
    }
    else {
      $output .= ' <'. $key .'>'. (is_array($value) ? format_xml_elements($value) : check_plain($value)) ."</$key>\n";
    }
  }
  return $output;
}

/**
 * Format a string containing a count of items.
 *
 * This function ensures that the string is pluralized correctly. Since t() is
 * called by this function, make sure not to pass already-localized strings to it.
 *
 * @param $count
 *   The item count to display.
 * @param $singular
 *   The string for the singular case. Please make sure it is clear this is
 *   singular, to ease translation (e.g. use "1 new comment" instead of "1 new").
 * @param $plural
 *   The string for the plural case. Please make sure it is clear this is plural,
 *   to ease translation. Use @count in place of the item count, as in "@count
 *   new comments".
 * @return
 *   A translated string.
 */
function format_plural($count, $singular, $plural) {
  if ($count == 1) return t($singular, array("@count" => $count));

  // get the plural index through the gettext formula
  $index = (function_exists('locale_get_plural')) ? locale_get_plural($count) : -1;
  if ($index < 0) { // backward compatibility
    return t($plural, array("@count" => $count));
  }
  else {
    switch ($index) {
      case "0":
        return t($singular, array("@count" => $count));
      case "1":
        return t($plural, array("@count" => $count));
      default:
        return t(strtr($plural, array("@count" => '@count['. $index .']')), array('@count['. $index .']' => $count));
    }
  }
}

/**
 * Generate a string representation for the given byte count.
 *
 * @param $size
 *   The size in bytes.
 * @return
 *   A translated string representation of the size.
 */
function format_size($size) {
  $suffix = t('bytes');
  if ($size >= 1024) {
    $size = round($size / 1024, 2);
    $suffix = t('KB');
  }
  if ($size >= 1024) {
    $size = round($size / 1024, 2);
    $suffix = t('MB');
  }
  return t('@size @suffix', array('@size' => $size, '@suffix' => $suffix));
}

/**
 * Format a time interval with the requested granularity.
 *
 * @param $timestamp
 *   The length of the interval in seconds.
 * @param $granularity
 *   How many different units to display in the string.
 * @return
 *   A translated string representation of the interval.
 */
function format_interval($timestamp, $granularity = 2) {
  $units = array('1 year|@count years' => 31536000, '1 week|@count weeks' => 604800, '1 day|@count days' => 86400, '1 hour|@count hours' => 3600, '1 min|@count min' => 60, '1 sec|@count sec' => 1);
  $output = '';
  foreach ($units as $key => $value) {
    $key = explode('|', $key);
    if ($timestamp >= $value) {
      $output .= ($output ? ' ' : '') . format_plural(floor($timestamp / $value), $key[0], $key[1]);
      $timestamp %= $value;
      $granularity--;
    }

    if ($granularity == 0) {
      break;
    }
  }
  return $output ? $output : t('0 sec');
}

/**
 * Format a date with the given configured format or a custom format string.
 *
 * Drupal allows administrators to select formatting strings for 'small',
 * 'medium' and 'large' date formats. This function can handle these formats,
 * as well as any custom format.
 *
 * @param $timestamp
 *   The exact date to format, as a UNIX timestamp.
 * @param $type
 *   The format to use. Can be "small", "medium" or "large" for the preconfigured
 *   date formats. If "custom" is specified, then $format is required as well.
 * @param $format
 *   A PHP date format string as required by date(). A backslash should be used
 *   before a character to avoid interpreting the character as part of a date
 *   format.
 * @param $timezone
 *   Time zone offset in seconds; if omitted, the user's time zone is used.
 * @return
 *   A translated date string in the requested format.
 */
function format_date($timestamp, $type = 'medium', $format = '', $timezone = NULL) {
  if (!isset($timezone)) {
    global $user;
    if (variable_get('configurable_timezones', 1) && $user->uid && strlen($user->timezone)) {
      $timezone = $user->timezone;
    }
    else {
      $timezone = variable_get('date_default_timezone', 0);
    }
  }

  $timestamp += $timezone;

  switch ($type) {
    case 'small':
      $format = variable_get('date_format_short', 'm/d/Y - H:i');
      break;
    case 'large':
      $format = variable_get('date_format_long', 'l, F j, Y - H:i');
      break;
    case 'custom':
      // No change to format
      break;
    case 'medium':
    default:
      $format = variable_get('date_format_medium', 'D, m/d/Y - H:i');
  }

  $max = strlen($format);
  $date = '';
  for ($i = 0; $i < $max; $i++) {
    $c = $format[$i];
    if (strpos('AaDFlM', $c) !== FALSE) {
      $date .= t(gmdate($c, $timestamp));
    }
    else if (strpos('BdgGhHiIjLmnsStTUwWYyz', $c) !== FALSE) {
      $date .= gmdate($c, $timestamp);
    }
    else if ($c == 'r') {
      $date .= format_date($timestamp - $timezone, 'custom', 'D, d M Y H:i:s O', $timezone);
    }
    else if ($c == 'O') {
      $date .= sprintf('%s%02d%02d', ($timezone < 0 ? '-' : '+'), abs($timezone / 3600), abs($timezone % 3600) / 60);
    }
    else if ($c == 'Z') {
      $date .= $timezone;
    }
    else if ($c == '\\') {
      $date .= $format[++$i];
    }
    else {
      $date .= $c;
    }
  }