Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/MathTrig.php
public static function SIGN($number)
    {
        $number = Functions::flattenSingleValue($number);

        if (is_bool($number)) {
            return (int) $number;
        }
        if (is_numeric($number)) {
            if ($number == 0.0) {
                return 0;
            }

            return $number / abs($number);
        }

        return Functions::VALUE();
    }
public static function SIGN($number)
    {
        $number = Functions::flattenSingleValue($number);

        if (is_bool($number)) {
            return (int) $number;
        }
        if (is_numeric($number)) {
            if ($number == 0.0) {
                return 0;
            }

            return $number / abs($number);
        }

        return Functions::VALUE();
    }
SIGN.

Determines the sign of a number. Returns 1 if the number is positive, zero (0)
if the number is 0, and -1 if the number is negative.

@param float $number Number to round

@return int sign value