Box\Spout\Reader\XLSX\Helper\StyleHelper::getFormatCodeForNumFmtId PHP Method

    protected function getFormatCodeForNumFmtId($numFmtId)
    {
        $customNumberFormats = $this->getCustomNumberFormats();
        // Using isset here because it is way faster than array_key_exists...
        return isset($customNumberFormats[$numFmtId]) ? $customNumberFormats[$numFmtId] : null;
    }