Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/MathTrig.php
public static function MOD($a = 1, $b = 1)
    {
        $a = (float) Functions::flattenSingleValue($a);
        $b = (float) Functions::flattenSingleValue($b);

        if ($b == 0.0) {
            return Functions::DIV0();
        } elseif (($a < 0.0) && ($b > 0.0)) {
            return $b - fmod(abs($a), $b);
        } elseif (($a > 0.0) && ($b < 0.0)) {
            return $b + fmod($a, abs($b));
        }

        return fmod($a, $b);
    }
public static function MOD($a = 1, $b = 1)
    {
        $a = (float) Functions::flattenSingleValue($a);
        $b = (float) Functions::flattenSingleValue($b);

        if ($b == 0.0) {
            return Functions::DIV0();
        } elseif (($a < 0.0) && ($b > 0.0)) {
            return $b - fmod(abs($a), $b);
        } elseif (($a > 0.0) && ($b < 0.0)) {
            return $b + fmod($a, abs($b));
        }

        return fmod($a, $b);
    }
MOD.

@param int $a Dividend
@param int $b Divisor

@return int Remainder