public function firstRow()
    {
        static $first;

        if (!$first) {
            $sheet = $this->sheet();
            $first = key($sheet);
        }

        return $first;
    }
public function firstRow()
    {
        static $first;

        if (!$first) {
            $sheet = $this->sheet();
            $first = key($sheet);
        }

        return $first;
    }
{@inheritDoc}
@link http://www.libxl.com/spreadsheet.html#lastRow