<?php
class Line {
	public $p1;
	public $p2;

	public function __construct(Vector $p1,Vector $p2) {
		$this->p1 = $p1;
		$this->p2 = $p2;
	}

	public function LengthSquared() {
		$dx = $this->p1->x - $this->p2->x;
		$dy = $this->p1->y - $this->p2->y;
		return $dx*$dx + $dy*$dy;
	}
	
	public function DistanceToPointSquared(Vector $point) {
		$v = new Vector($point->x - $this->p1->x, $point->y - $this->p1->y);
		$l = new Vector($this->p2->x - $this->p1->x, $this->p2->y - $this->p1->y);
		$dot = $v->DotProduct($l->UnitVector());
		if ($dot <= 0) {// Point nearest P1
			$dl = new Line($this->p1, $point);
			return $dl->LengthSquared();
		}
		if (($dot*$dot)>=$this->LengthSquared()) {// Point nearest P2
			$dl = new Line($this->p2, $point);
			return $dl->LengthSquared();
		} else {// Point within line
			$v2 = new Line($this->p1, $point);
			$h = $v2->LengthSquared();
			return $h - $dot * $dot;
		}
	}
}
?>