php类的继承

<?php
/*
 * 类的继承(extends):
 * 指可以创建一个新的类，该类继承(extends) 了父类的属性和方法，并且可以添加自己的属性和方法
*/
class Animal {
    public string $name = 'neko';
    protected int $age = 20;
    private string $birth = '2020-02-11';
}

class Dog extends Animal {
    public function setAge(int $age): void
    {
        $this->age = $age;
        echo $this->age;
    }
}

//var_dump(new Animal());
$dog = new Dog();
echo $dog->name . "\n";
$dog->setAge(2);