Views Contextual filter values to display a list of users with today's birthday

views3_birthdays

$results = db_query("SELECT entity_id FROM field_data_field_birthday WHERE DATE_FORMAT(field_birthday_value,'%m-%d') = DATE_FORMAT(NOW(),'%m-%d') AND entity_type = 'user'");
$ids = array();
foreach ($results as $result) {
  $ids[] = $result->entity_id;
}
return implode(',',$ids);