public function getPerimeter()
{
$return = null;
if (count($this->points) >= 2) {
$perimeterPoints = $this->points;
$perimeterPoints[] = $perimeterPoints[0];
$perimeter = 0;
for ($i = 0; $i < count($this->points); $i++) {
$perimeter += Point::distance($perimeterPoints[$i], $perimeterPoints[$i + 1]);
}
$return = $perimeter;
}
return $return;
}