LMongo\Query\Builder::addToSet PHP Method

    public function addToSet($column, $value = null)
    {
        if (is_array($column)) {
            $update = array('$addToSet' => $column);
        } else {
            $update = array('$addToSet' => array($column => $value));
        }
        return $this->performUpdate($update);
    }