og_context.module.php

function c4m_og_access() {
  if (!og_context_is_init()) {
    // OG context wasn't called yet, so we can't call og_context() ourself yet.
    return;
  }

  if (!$og_context = og_context()) {
    // No OG context.
    return;
  }
}

/**
 * Determines if OG context has been already called.
 */
function og_context_is_init($called = FALSE) {
  $return = &drupal_static(__FUNCTION__, FALSE);

  if ($called) {
    $return = $called;
  }

  return $return;
}



/**
 * Get or set group context using the menu system.
 * @param $group_type
 *   The context to get by group type. Defaults to "node".
 * @param $group
 *   Optional; The group entity to set as the context.
 * @param $account
 *   Optional; The user entity we are getting context for. If empty - defaults
 *   to current user.
 * @param bool $check_access
 *   Determines if access to the group should be done. Defaults to TRUE.
 *
 * @return array
 *   Array keyed by the group type and group ID, or FALSE if no context
 *   was found.
 */
function og_context($group_type = 'node', $group = NULL, $account = NULL, $check_access = TRUE) {
  global $user;
  // User account is sent.
  $account = $account ? $account : user_load($user->uid);

  $context = &drupal_static(__FUNCTION__, FALSE);

  if (empty($group) && $context !== FALSE) {
    og_context_is_init(TRUE);

    // Determine if we can return cached values.
    if (empty($context)) {
      // We already tried to find a context, but couldn't.
      return FALSE;
    }

    if ($context['group_type'] == $group_type) {
      // Return the cached values.
      return $context;
    }
  }

  // Set the context to array, so we can know this function has been already
  // executed.
  $context = array();

  if (!empty($group)) {
    og_context_is_init(TRUE);
    if (!og_is_group($group_type, $group)) {
      // The passed entity isn't a valid group.
      return FALSE;
    }

    if ($check_access && !entity_access('view', $group_type, $group, $account)) {
      // User doesn't have access to the group.
      return FALSE;
    }

    list($id) = entity_extract_ids($group_type, $group);
    $context = array('group_type' => $group_type, 'gid' => $id);
  }
  // Get context from context handlers.
  elseif ($gid = og_context_determine_context($group_type, NULL, $check_access)) {
    og_context_is_init(TRUE);
    $context = array('group_type' => $group_type, 'gid' => $gid);
    if ($user->uid) {
      // Save the group ID in the authenticated user's session.
      $_SESSION['og_context'] = array('group_type' => $group_type, 'gid' => $gid);
    }
  }

  return $context;
}