Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/MathTrig.php
public static function TRUNC($value = 0, $digits = 0)
    {
        $value = Functions::flattenSingleValue($value);
        $digits = Functions::flattenSingleValue($digits);

        // Validate parameters
        if ((!is_numeric($value)) || (!is_numeric($digits))) {
            return Functions::VALUE();
        }
        $digits = floor($digits);

        // Truncate
        $adjust = pow(10, $digits);

        if (($digits > 0) && (rtrim((int) ((abs($value) - abs((int) $value)) * $adjust), '0') < $adjust / 10)) {
            return $value;
        }

        return ((int) ($value * $adjust)) / $adjust;
    }
public static function TRUNC($value = 0, $digits = 0)
    {
        $value = Functions::flattenSingleValue($value);
        $digits = Functions::flattenSingleValue($digits);

        // Validate parameters
        if ((!is_numeric($value)) || (!is_numeric($digits))) {
            return Functions::VALUE();
        }
        $digits = floor($digits);

        // Truncate
        $adjust = pow(10, $digits);

        if (($digits > 0) && (rtrim((int) ((abs($value) - abs((int) $value)) * $adjust), '0') < $adjust / 10)) {
            return $value;
        }

        return ((int) ($value * $adjust)) / $adjust;
    }
TRUNC.

Truncates value to the number of fractional digits by number_digits.

@param float $value
@param int $digits

@return float Truncated value