How can abstract classes in PHP help in avoiding the need to implement functions in every derived class?

When we have a common set of methods that need to be implemented in multiple classes, we can use abstract classes in PHP to define these methods without providing an implementation. This way, we can avoid the need to implement the same functions in every derived class, saving time and reducing code duplication. 

<?php

abstract class Shape {
    abstract public function calculateArea();
    abstract public function calculatePerimeter();
}

class Circle extends Shape {
    private $radius;

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

    public function calculateArea() {
        return pi() * pow($this->radius, 2);
    }

    public function calculatePerimeter() {
        return 2 * pi() * $this->radius;
    }
}

class Square extends Shape {
    private $sideLength;

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

    public function calculateArea() {
        return pow($this->sideLength, 2);
    }

    public function calculatePerimeter() {
        return 4 * $this->sideLength;
    }
}

$circle = new Circle(5);
echo "Circle Area: " . $circle->calculateArea() . "\n";
echo "Circle Perimeter: " . $circle->calculatePerimeter() . "\n";

$square = new Square(4);
echo "Square Area: " . $square->calculateArea() . "\n";
echo "Square Perimeter: " . $square->calculatePerimeter() . "\n";
?>

Keywords

abstract classes inheritance polymorphism OOP code reusability

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