Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Cell/DataValidator.php
public function isValid(Cell $cell)
    {
        if (!$cell->hasDataValidation()) {
            return true;
        }

        $cellValue = $cell->getValue();
        $dataValidation = $cell->getDataValidation();

        if (!$dataValidation->getAllowBlank() && ($cellValue === null || $cellValue === '')) {
            return false;
        }

        // TODO: write check on all cases
        switch ($dataValidation->getType()) {
            case DataValidation::TYPE_LIST:
                return $this->isValueInList($cell);
        }

        return false;
    }
public function isValid(Cell $cell)
    {
        if (!$cell->hasDataValidation()) {
            return true;
        }

        $cellValue = $cell->getValue();
        $dataValidation = $cell->getDataValidation();

        if (!$dataValidation->getAllowBlank() && ($cellValue === null || $cellValue === '')) {
            return false;
        }

        // TODO: write check on all cases
        switch ($dataValidation->getType()) {
            case DataValidation::TYPE_LIST:
                return $this->isValueInList($cell);
        }

        return false;
    }
Does this cell contain valid value?

@param Cell $cell Cell to check the value

@return bool