/**
* save a child user of current user
* @param int id of child user
* @return void
*/
public function saveChild($id_child = 0)
{
$user_child = new UserChild();
$user_child->user_id = Yii::app()->user->id;
$user_child->user_child_id = $id_child;
$user_child->save();
}
