code: 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();
      }
docs: 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