Doctrine\MongoDB\Query\Builder::select PHP Method

    public function select($fieldName = null)
    {
        if (!isset($this->query['select'])) {
            $this->query['select'] = [];
        }
        $fieldNames = is_array($fieldName) ? $fieldName : func_get_args();
        foreach ($fieldNames as $fieldName) {
            $this->query['select'][$fieldName] = 1;
        }
        return $this;
    }