Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Reader/Xls.php
private function readBoolErr()
    {
        $length = self::getUInt2d($this->data, $this->pos + 2);
        $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);

        // move stream pointer to next record
        $this->pos += 4 + $length;

        // offset: 0; size: 2; row index
        $row = self::getUInt2d($recordData, 0);

        // offset: 2; size: 2; column index
        $column = self::getUInt2d($recordData, 2);
        $columnString = Coordinate::stringFromColumnIndex($column + 1);

        // Read cell?
        if (($this->getReadFilter() !== null) && $this->getReadFilter()->readCell($columnString, $row + 1, $this->phpSheet->getTitle())) {
            // offset: 4; size: 2; index to XF record
            $xfIndex = self::getUInt2d($recordData, 4);

            // offset: 6; size: 1; the boolean value or error value
            $boolErr = ord($recordData[6]);

            // offset: 7; size: 1; 0=boolean; 1=error
            $isError = ord($recordData[7]);

            $cell = $this->phpSheet->getCell($columnString . ($row + 1));
            switch ($isError) {
                case 0: // boolean
                    $value = (bool) $boolErr;

                    // add cell value
                    $cell->setValueExplicit($value, DataType::TYPE_BOOL);

                    break;
                case 1: // error type
                    $value = Xls\ErrorCode::lookup($boolErr);

                    // add cell value
                    $cell->setValueExplicit($value, DataType::TYPE_ERROR);

                    break;
            }

            if (!$this->readDataOnly) {
                // add cell style
                $cell->setXfIndex($this->mapCellXfIndex[$xfIndex]);
            }
        }
    }
private function readBoolErr()
    {
        $length = self::getUInt2d($this->data, $this->pos + 2);
        $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);

        // move stream pointer to next record
        $this->pos += 4 + $length;

        // offset: 0; size: 2; row index
        $row = self::getUInt2d($recordData, 0);

        // offset: 2; size: 2; column index
        $column = self::getUInt2d($recordData, 2);
        $columnString = Coordinate::stringFromColumnIndex($column + 1);

        // Read cell?
        if (($this->getReadFilter() !== null) && $this->getReadFilter()->readCell($columnString, $row + 1, $this->phpSheet->getTitle())) {
            // offset: 4; size: 2; index to XF record
            $xfIndex = self::getUInt2d($recordData, 4);

            // offset: 6; size: 1; the boolean value or error value
            $boolErr = ord($recordData[6]);

            // offset: 7; size: 1; 0=boolean; 1=error
            $isError = ord($recordData[7]);

            $cell = $this->phpSheet->getCell($columnString . ($row + 1));
            switch ($isError) {
                case 0: // boolean
                    $value = (bool) $boolErr;

                    // add cell value
                    $cell->setValueExplicit($value, DataType::TYPE_BOOL);

                    break;
                case 1: // error type
                    $value = Xls\ErrorCode::lookup($boolErr);

                    // add cell value
                    $cell->setValueExplicit($value, DataType::TYPE_ERROR);

                    break;
            }

            if (!$this->readDataOnly) {
                // add cell style
                $cell->setXfIndex($this->mapCellXfIndex[$xfIndex]);
            }
        }
    }
Read BOOLERR record
This record represents a Boolean value or error value
cell.

--    "OpenOffice.org's Documentation of the Microsoft
Excel File Format"