PHP のオブジェクト演算子 (`->` および `::`) はどのように機能しますか?

$object->property;
$object->method();

class Person {
    private $name;
    public function sayHello() {
        return "Hello, my name is " . $this->name;
    }
}

$person = new Person();
$person->name = "John Doe";
echo $person->sayHello(); // Output: "Hello, my name is John Doe"

class Math {
    public static function add($a, $b) {
        return $a + $b;
    }
}

$result = Math::add(5, 10); // Output: 15

class Counter {
    public static $count = 0;
    public function increment() {
        self::$count++;
    }
}

Counter::increment(); // Increment the static $count
echo Counter::$count; // Output: 1

class Animal {
    public function move() {
        //...
    }
}

class Dog extends Animal {
    public function bark() {
        // Call the move() method from the parent class using ::
        parent::move();
    }
}