public function findByIdSet($idSet)
{
$ids = Arrays::toStringSQL($idSet, ",");
$sql = "SELECT id, login, firstname, lastname, email, online, gender, birthdate, avatar, lastActive\n\t\t\t\tFROM user \n\t\t\t\tWHERE id in ({$ids})";
$users = $this->execute($sql);
return $result = count($users) > 0 ? $users : null;
}