Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Cell/DataValidator.php
private function isValueInList(Cell $cell)
    {
        $cellValue = $cell->getValue();
        $dataValidation = $cell->getDataValidation();

        $formula1 = $dataValidation->getFormula1();
        if (!empty($formula1)) {
            // inline values list
            if ($formula1[0] === '"') {
                return in_array(strtolower($cellValue), explode(',', strtolower(trim($formula1, '"'))), true);
            } elseif (strpos($formula1, ':') > 0) {
                // values list cells
                $matchFormula = '=MATCH(' . $cell->getCoordinate() . ', ' . $formula1 . ', 0)';
                $calculation = Calculation::getInstance($cell->getWorksheet()->getParent());

                try {
                    $result = $calculation->calculateFormula($matchFormula, $cell->getCoordinate(), $cell);

                    return $result !== Functions::NA();
                } catch (Exception $ex) {
                    return false;
                }
            }
        }

        return true;
    }
private function isValueInList(Cell $cell)
    {
        $cellValue = $cell->getValue();
        $dataValidation = $cell->getDataValidation();

        $formula1 = $dataValidation->getFormula1();
        if (!empty($formula1)) {
            // inline values list
            if ($formula1[0] === '"') {
                return in_array(strtolower($cellValue), explode(',', strtolower(trim($formula1, '"'))), true);
            } elseif (strpos($formula1, ':') > 0) {
                // values list cells
                $matchFormula = '=MATCH(' . $cell->getCoordinate() . ', ' . $formula1 . ', 0)';
                $calculation = Calculation::getInstance($cell->getWorksheet()->getParent());

                try {
                    $result = $calculation->calculateFormula($matchFormula, $cell->getCoordinate(), $cell);

                    return $result !== Functions::NA();
                } catch (Exception $ex) {
                    return false;
                }
            }
        }

        return true;
    }
Does this cell contain valid value, based on list?

@param Cell $cell Cell to check the value

@return bool