Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Engineering.php
public static function DECTOBIN($x, $places = null)
    {
        $x = Functions::flattenSingleValue($x);
        $places = Functions::flattenSingleValue($places);

        if (is_bool($x)) {
            if (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_OPENOFFICE) {
                $x = (int) $x;
            } else {
                return Functions::VALUE();
            }
        }
        $x = (string) $x;
        if (strlen($x) > preg_match_all('/[-0123456789.]/', $x, $out)) {
            return Functions::VALUE();
        }

        $x = (string) floor($x);
        if ($x < -512 || $x > 511) {
            return Functions::NAN();
        }

        $r = decbin($x);
        // Two's Complement
        $r = substr($r, -10);
        if (strlen($r) >= 11) {
            return Functions::NAN();
        }

        return self::nbrConversionFormat($r, $places);
    }
public static function DECTOBIN($x, $places = null)
    {
        $x = Functions::flattenSingleValue($x);
        $places = Functions::flattenSingleValue($places);

        if (is_bool($x)) {
            if (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_OPENOFFICE) {
                $x = (int) $x;
            } else {
                return Functions::VALUE();
            }
        }
        $x = (string) $x;
        if (strlen($x) > preg_match_all('/[-0123456789.]/', $x, $out)) {
            return Functions::VALUE();
        }

        $x = (string) floor($x);
        if ($x < -512 || $x > 511) {
            return Functions::NAN();
        }

        $r = decbin($x);
        // Two's Complement
        $r = substr($r, -10);
        if (strlen($r) >= 11) {
            return Functions::NAN();
        }

        return self::nbrConversionFormat($r, $places);
    }
DECTOBIN.

Return a decimal value as binary.

Excel Function:
DEC2BIN(x[,places])

@category Engineering Functions

@param string $x The decimal integer you want to convert. If number is negative,
valid place values are ignored and DEC2BIN returns a 10-character
(10-bit) binary number in which the most significant bit is the sign
bit. The remaining 9 bits are magnitude bits. Negative numbers are
represented using two's-complement notation.
If number < -512 or if number > 511, DEC2BIN returns the #NUM! error
value.
If number is nonnumeric, DEC2BIN returns the #VALUE! error value.
If DEC2BIN requires more than places characters, it returns the #NUM!
error value.
@param int $places The number of characters to use. If places is omitted, DEC2BIN uses
the minimum number of characters necessary. Places is useful for
padding the return value with leading 0s (zeros).
If places is not an integer, it is truncated.
If places is nonnumeric, DEC2BIN returns the #VALUE! error value.
If places is zero or negative, DEC2BIN returns the #NUM! error value.

@return string