Polygon::getArea PHP Method

    public function getArea()
    {
        $return = null;
        if (count($this->points) >= 3) {
            $areaPoints = $this->points;
            $areaPoints[] = $areaPoints[0];
            $area = 0;
            for ($i = 0; $i < count($this->points); $i++) {
                $area += $areaPoints[$i]->x * $areaPoints[$i + 1]->y;
                $area -= $areaPoints[$i + 1]->x * $areaPoints[$i]->y;
            }
            $return = abs($area / 2);
        }
        return $return;
    }