public function lastRow()
    {
        static $last;

        if (!$last) {
            $sheet = $this->sheet();
            end($sheet);
            $last = key($sheet) + 1;
        }

        return $last;
    }
public function lastRow()
    {
        static $last;

        if (!$last) {
            $sheet = $this->sheet();
            end($sheet);
            $last = key($sheet) + 1;
        }

        return $last;
    }
{@inheritDoc}