Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Cell/DataType.php
public static function checkErrorCode($pValue)
    {
        $pValue = (string) $pValue;

        if (!isset(self::$errorCodes[$pValue])) {
            $pValue = '#NULL!';
        }

        return $pValue;
    }
public static function checkErrorCode($pValue)
    {
        $pValue = (string) $pValue;

        if (!isset(self::$errorCodes[$pValue])) {
            $pValue = '#NULL!';
        }

        return $pValue;
    }
Check a value that it is a valid error code.

@param mixed $pValue Value to sanitize to an Excel error code

@return string Sanitized value