function _calculateCellLengths($row) {
        for ($i = 0; $i < count($row); $i++) {
            if (!isset($this->_cell_lengths[$i])) {
                $this->_cell_lengths[$i] = 0;
            }
            $this->_cell_lengths[$i] = max($this->_cell_lengths[$i],
                $this->_strlen($row[$i]));
        }
    }