/** * Sets the recipient mode of the API call to either `single` or `all` based on the audience we want to send the * push notification to. * * Note: if the recipient mode is set to `single`, we require a device token to be set with `set_device_token`. * * @param string $mode * @return bool */ public static function set_recipient_mode($mode = 'all') { if ($mode !== 'all' && $mode !== 'single') { return false; } self::$_recipient_mode = $mode; return true; }