code: public static function POWER($x = 0, $y = 2)
      {
          $x = Functions::flattenSingleValue($x);
          $y = Functions::flattenSingleValue($y);
  
          // Validate parameters
          if ($x == 0.0 && $y == 0.0) {
              return Functions::NAN();
          } elseif ($x == 0.0 && $y < 0.0) {
              return Functions::DIV0();
          }
  
          // Return
          $result = pow($x, $y);
  
          return (!is_nan($result) && !is_infinite($result)) ? $result : Functions::NAN();
      }
docs: POWER.
  
  Computes x raised to the power y.
  
  @param float $x
  @param float $y
  
  @return float