PHP class with comparable interface

PHP OOP: Exercise-12 with Solution

Write a class called 'Product' with properties like 'name' and 'price'. Implement the 'Comparable' interface to compare products based on their prices.

Sample Solution:

PHP Code :

interface Comparable {
    public function compareTo($other);

class Product implements Comparable {
    private $name;
    private $price;

    public function __construct($name, $price) {
        $this->name = $name;
        $this->price = $price;

    public function getName() {
        return $this->name;

    public function getPrice() {
        return $this->price;

    public function compareTo($other) {
        if ($other instanceof Product) {
            if ($this->price < $other->getPrice()) {
                return -1;
            } elseif ($this->price > $other->getPrice()) {
                return 1;
            } else {
                return 0;
        } else {
            throw new Exception("Invalid comparison object.");

$product1 = new Product("Desktop", 1200);
$product2 = new Product("Laptop", 1000);

$result = $product1->compareTo($product2);

if ($result < 0) {
    echo $product1->getName() . " is cheaper than " . $product2->getName() . "</br>";
} elseif ($result > 0) {
    echo $product1->getName() . " is more expensive than " . $product2->getName() . "</br>";
} else {
    echo $product1->getName() . " and " . $product2->getName() . " have the same price.</br>";


Sample Output:

Desktop is more expensive than Laptop


In the above exercise -

  • The Comparable interface declares a single method compareTo() that accepts another object for comparison.
  • The "Product" class implements the Comparable interface and defines the compareTo() method.
  • The Product class has two private properties: $name and $price, representing the product's name and price.
  • The constructor method __construct() is used to initialize the values of the properties when creating a new instance of the Product class.
  • The getName() and getPrice() methods retrieve name and price, respectively.
  • The compareTo() method compares two Product objects based on their prices. It returns -1, 0, or 1 indicating whether the current object is less than, equal to, or greater than the compared object.


Flowchart: PHP class with comparable interface.
Flowchart: PHP class with comparable interface.

PHP Code Editor:

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