Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/TextData.php
public static function TRIMNONPRINTABLE($stringValue = '')
    {
        $stringValue = Functions::flattenSingleValue($stringValue);

        if (is_bool($stringValue)) {
            return ($stringValue) ? Calculation::getTRUE() : Calculation::getFALSE();
        }

        if (self::$invalidChars == null) {
            self::$invalidChars = range(chr(0), chr(31));
        }

        if (is_string($stringValue) || is_numeric($stringValue)) {
            return str_replace(self::$invalidChars, '', trim($stringValue, "\x00..\x1F"));
        }

        return null;
    }
public static function TRIMNONPRINTABLE($stringValue = '')
    {
        $stringValue = Functions::flattenSingleValue($stringValue);

        if (is_bool($stringValue)) {
            return ($stringValue) ? Calculation::getTRUE() : Calculation::getFALSE();
        }

        if (self::$invalidChars == null) {
            self::$invalidChars = range(chr(0), chr(31));
        }

        if (is_string($stringValue) || is_numeric($stringValue)) {
            return str_replace(self::$invalidChars, '', trim($stringValue, "\x00..\x1F"));
        }

        return null;
    }
TRIMNONPRINTABLE.

@param mixed $stringValue Value to check

@return string