PHP interface resizable: Resizing functionality in the square class

PHP OOP: Exercise-4 with Solution

Write a PHP interface called 'Resizable' with a method 'resize()'. Implement the 'Resizable' interface in a class called 'Square' and add functionality to resize the square.

Sample Solution:

PHP Code :

interface Resizable {
    public function resize($percentage);

class Square implements Resizable {
    private $side;

    public function __construct($side) {
        $this->side = $side;

    public function resize($percentage) {
        $this->side = $this->side * ($percentage / 100);

    public function getArea() {
        return pow($this->side, 2);

    public function getSide() {
        return $this->side;

$square = new Square(10);
echo "Initial Side Length: " . $square->getSide() . "</br>";

$square->resize(60); // Resize the square to 60% of its original size
echo "Resized Side Length: " . $square->getSide() . "</br>";

echo "Area: " . $square->getArea() . "</br>";

Sample Output:

Initial Side Length: 10
Resized Side Length: 6
Area: 36


In the above exercise -

  • The Resizable interface defines a contract with a single method resize(). Any class that implements this interface must implement the resize() method.
  • The "Square" class implements the Resizable interface and provides its own implementation for the resize() method. It also has a private property $side to represent the sides of the square.
  • The resize() method in the Square class resizes the square by adjusting its side length based on the provided percentage.
  • The getArea() method calculates and returns the square area using the formula: side * side.
  • The getSide() method returns the current square side length.


Flowchart: Resizing functionality in the square class.
Flowchart: Resizing functionality in the square class.

PHP Code Editor:

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