point.php

class Point {
    private $x;
    private $y;
    private $z;

    public function __construct(int $x, int $y, int $z) {
        $this->x = $x;
        $this->y = $y;
        $this->z = $z;
    }

    public function distance(Point $point):float {
        return sqrt(
            pow($point->x - $this->x, 2) +
            pow($point->y - $this->y, 2) +
            pow($point->z - $this->z, 2));
    }
}

$pointA = new Point(0, -3, 3);
$pointB = new Point(3, 1, 3);
echo $pointA->distance($pointB);