PHP基础-类的继承使用01

<?php
/**
 * Created by PhpStorm.
 */

class people
{
    private $name = '';
    private $age = 0;
    function __construct($n,$a)
    {
        $this->name = $n;
        $this->age = $a;
    }

    function intro()
    {
        return "my name is {$this->name}, i am {$this->age} years old.<br>";
    }

    function get_name()
    {
        return $this->name;
    }

    function get_age()
    {
        return $this->age;
    }
}

class student extends people
{

}

$stu = new student('wangfu',21);
if($stu instanceof student)
{
    echo "stu is a student class.<br>";
}

if($stu instanceof people)
{
    echo "stu is a people class.<br>";
}