Mixpanel

/**
 * Returns default properties sent with every event for a user.
 *
 * During a single request, it will cache the default properties for
 * a given user account.
 *
 * @param object $account
 *   (optional) The user these defaults are for. If not given, the currently
 *   logged in user will be used.
 * @param bool $reset
 *   (optional) If set to TRUE, the cache will be cleared and fresh data will be
 *   returned.
 *
 * @return array
 *   Array of the default mixpanel variables.
 *
 * @see hook_mixpanel_default_alter()
 * @see mixpanel_track()
 *
 * @ingroup mixpanel
 */
function mixpanel_get_defaults($account = NULL, $reset = FALSE) {
  global $user;

  $defaults =& drupal_static(__FUNCTION__, array());

  // If user object is passed in, favor that, otherwise, set $account to the
  // current object.
  if (is_null($account)) {
    $account = $user;
  }

  if (!isset($defaults[$account->uid]) || $reset) {
    $properties = array(
      'ip' => ip_address(),
      '$browser' => _mixpanel_get_browser(),
      '$os' => _mixpanel_get_os(),
      '$device' => _mixpanel_get_device(),
      '$referrer' => $_SERVER['HTTP_REFERER'],
      '$referring_domain' => parse_url($_SERVER['HTTP_REFERER'], PHP_URL_HOST),
    );

    // For authenticated users.
    if ($account->uid != 0) {
      $properties = array_merge($properties, array(
        'uid' => $account->uid,
        'mp_name_tag' => $account->name,
        'distinct_id' => $account->uid,
      ));
    }

    // Let other modules alter the defaults.
    drupal_alter('mixpanel_defaults', $properties, $account);

    $defaults[$account->uid] = $properties;
  }

  return $defaults[$account->uid];
}