What are the differences between object-oriented programming in Java and PHP?

Object-oriented programming in Java and PHP share many similarities, such as the use of classes, objects, inheritance, and encapsulation. However, there are some key differences between the two languages. One major difference is that Java is a statically-typed language, meaning that data types are explicitly declared at compile time, while PHP is dynamically-typed, allowing for more flexibility with variable types. Additionally, Java uses interfaces for defining contracts between classes, while PHP uses abstract classes for similar purposes. Lastly, Java has strict access modifiers (public, private, protected), while PHP has less strict visibility modifiers.

// PHP code snippet demonstrating the use of abstract classes in PHP
abstract class Shape {
    protected $color;

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

    abstract public function calculateArea();
}

class Circle extends Shape {
    private $radius;

    public function __construct($color, $radius) {
        parent::__construct($color);
        $this->radius = $radius;
    }

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

$circle = new Circle("red", 5);
echo $circle->calculateArea(); // Output: 78.54