/**
* 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;
}
