Challenge 3 — Solution

Task: Create a Rectangle class with a constructor taking $width and
$height, and methods getArea() and getPerimeter(). Create two
rectangles with different dimensions and echo both calculated values
for each, demonstrating they're independent of one another.

<?php
    class Rectangle {
        public function __construct(
            private float $width,
            private float $height
        ) {}

        public function getArea(): float {
            return $this->width * $this->height;
        }

        public function getPerimeter(): float {
            return 2 * ($this->width + $this->height);
        }
    }

    $rect1 = new Rectangle(4, 6);
    $rect2 = new Rectangle(10, 2.5);

    echo "Rectangle 1 - Area: " . $rect1->getArea() . ", Perimeter: " . $rect1->getPerimeter() . "<br>";
    echo "Rectangle 2 - Area: " . $rect2->getArea() . ", Perimeter: " . $rect2->getPerimeter();
?>


Output:
Rectangle 1 - Area: 24, Perimeter: 20
Rectangle 2 - Area: 25, Perimeter: 25

Notes:
- This solution uses constructor property promotion (the shorthand
  mentioned in the chapter's own tip-box) - adding "private" directly
  in front of $width and $height in the constructor's parameter list
  automatically creates and assigns both properties, with no separate
  $this->width = $width; lines needed.
- $rect1 and $rect2 are entirely independent objects - each has its own
  $width and $height, so calling getArea() or getPerimeter() on one has
  no effect whatsoever on the other's stored values.
- Rectangle 2 happens to have identical area and perimeter (25 and 25)
  purely by coincidence of the chosen dimensions - both methods are
  still computed completely independently from $width and $height.