session_cache.module in Session Cache API 6

session_cache.module

A pluggable user session access facility for programmers who want a simple two-function API that is independent of the actual storage mechanism. Used in particular to avoid $_SESSION as the storage mechanism, so that anonymous user sessions can be used in the context of Varnish.

The database storage mechanism uses core's cache.inc.

See README.txt for details.

File

session_cache.module

<?php

/**
 * @file
 * session_cache.module
 *
 * A pluggable user session access facility for programmers who want a simple
 * two-function API that is independent of the actual storage mechanism.
 * Used in particular to avoid $_SESSION as the storage mechanism, so that
 * anonymous user sessions can be used in the context of Varnish.
 *
 * The database storage mechanism uses core's cache.inc.
 *
 * See README.txt for details.
 */
define('SESSION_CACHE_STORAGE_COOKIE', 3);
define('SESSION_CACHE_STORAGE_DB_CORE', 2);
define('SESSION_CACHE_STORAGE_SESSION', 1);
define('SESSION_CACHE_DEFAULT_EXPIRATION_DAYS', 7);

/**
 * Write the supplied data to the user session, whatever the storage mechanism may be.
 *
 * @param string $bin, unique id eg a string prefixed by the module name
 * @param $data, use NULL to delete the bin; it may be refilled at any time
 */
function session_cache_set($bin, $data) {
  if (!isset($bin)) {
    return;
  }
  $method = variable_get('session_cache_storage_method', SESSION_CACHE_STORAGE_SESSION);
  switch ($method) {
    case SESSION_CACHE_STORAGE_COOKIE:

      // Tell the browser to return the cookie only via HTTP or HTTPS, to any
      // path under the root of this server.
      // Don't use "global $cookie_domain", as it may contain the invalid '.localhost'!
      $cookie_domain = ini_get('session.cookie_domain');
      $serialized_data = $data == NULL ? NULL : serialize($data);
      setcookie("Drupal.session_cache.{$bin}", $serialized_data, $data == NULL ? 0 : session_cache_expiration_time(), '/', $cookie_domain, NULL, TRUE);

      // Make sure that subsequent session_cache_get() calls get the data
      // updated here, not what was in the cookie at the start of the request!
      // Note that in array indices '.' are converted to '_'
      $_COOKIE["Drupal_session_cache_{$bin}"] = $serialized_data;
      return;
    case SESSION_CACHE_STORAGE_DB_CORE:
      $sid = session_cache_get_sid();
      if ($data == NULL) {
        cache_clear_all("{$bin}:{$sid}", 'cache_session_cache');
      }
      else {
        cache_set("{$bin}:{$sid}", $data, 'cache_session_cache', session_cache_expiration_time());
      }
      return;
    case SESSION_CACHE_STORAGE_SESSION:
      if ($data == NULL) {
        unset($_SESSION[$bin]);
        return;
      }
      $_SESSION[$bin] = $data;
      return;
    default:
      module_invoke_all('session_cache_set', $method, $bin, $data);
  }
}

/**
 * Read data from the user session, given its bin id.
 *
 * @param $bin
 */
function session_cache_get($bin) {
  if (!isset($bin)) {
    return NULL;
  }
  $method = variable_get('session_cache_storage_method', SESSION_CACHE_STORAGE_SESSION);
  switch ($method) {
    case SESSION_CACHE_STORAGE_COOKIE:

      // Note that in array indices '.' are converted to '_'
      return isset($_COOKIE['Drupal_session_cache_' . $bin]) ? unserialize($_COOKIE['Drupal_session_cache_' . $bin]) : NULL;
    case SESSION_CACHE_STORAGE_DB_CORE:
      $sid = session_cache_get_sid();
      $cache = cache_get("{$bin}:{$sid}", 'cache_session_cache');
      return is_object($cache) ? $cache->data : NULL;
    case SESSION_CACHE_STORAGE_SESSION:
      return isset($_SESSION) && isset($_SESSION[$bin]) ? $_SESSION[$bin] : NULL;
    default:
      return module_invoke_all('session_cache_get', $method, $bin);
  }
}

/**
 * Implements hook_cron().
 */
function session_cache_cron() {
  if (variable_get('session_cache_storage_method', SESSION_CACHE_STORAGE_SESSION) == SESSION_CACHE_STORAGE_DB_CORE) {

    // Delete only the expired cache_session_cache entries.
    // Note: to avoid the clear() function setting $_SESSION['cache_expiration'][..],
    // the cache lifetime should not be configured, ie cache_lifetime==0.
    // This will also stop the cache's garbage collection.
    cache_clear_all(NULL, 'cache_session_cache');
  }
}

/**
 * Returns an identifier for the current user session.
 *
 * Typically only called when a database storage mechanism is used.
 *
 * @return sid
 */
function session_cache_get_sid() {
  global $user;
  if (!empty($user->uid) && variable_get('session_cache_use_uid_as_sid', FALSE)) {
    return 'user' . $user->uid;

    // good if concurrent sessions for the same authenticated user are NOT required
  }
  if (empty($_COOKIE['Drupal_session_cache_sid'])) {

    // Don't use core's session id. Security not a problem, so keep it short.
    $sid = drupal_substr(session_id(), 0, 12);

    // Don't use "global $cookie_domain", as '.localhost' is invalid!
    $cookie_domain = ini_get('session.cookie_domain');

    // If setcookie() fails, then everything still works, but a new session will
    // be created when logging in or out.
    setcookie('Drupal.session_cache.sid', $sid, session_cache_expiration_time(), '/', $cookie_domain, NULL, TRUE);
  }
  else {
    $sid = $_COOKIE['Drupal_session_cache_sid'];
  }
  return $sid;
}
function session_cache_expiration_time() {
  return REQUEST_TIME + 24 * 60 * 60 * variable_get('session_cache_expire_period', SESSION_CACHE_DEFAULT_EXPIRATION_DAYS);
}

/**
 * Implements hook_menu().
 */
function session_cache_menu() {
  $items['admin/settings/session_cache'] = array(
    'title' => 'Session Cache API',
    'description' => 'Select the session storage mechanism.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array(
      'session_cache_admin_config',
    ),
    'access arguments' => array(
      'administer site configuration',
    ),
    'file' => 'session_cache.admin.inc',
  );
  return $items;
}

Functions

Name	Description
session_cache_cron	Implements hook_cron().
session_cache_expiration_time
session_cache_get	Read data from the user session, given its bin id.
session_cache_get_sid	Returns an identifier for the current user session.
session_cache_menu	Implements hook_menu().
session_cache_set	Write the supplied data to the user session, whatever the storage mechanism may be.

Constants

Name	Description
SESSION_CACHE_DEFAULT_EXPIRATION_DAYS
SESSION_CACHE_STORAGE_COOKIE	@file session_cache.module
SESSION_CACHE_STORAGE_DB_CORE
SESSION_CACHE_STORAGE_SESSION