<?php

class Car {

    private $speed = 0;

    public function getSpeed() {

        return $this->speed;

    }

    protected function speedUp() {

        $this->speed += 10;

    }

    //增加start方法，使他能够调用受保护的方法speedUp实现加速10

    public function start(){

        $this->speedUp();

    }

}

$car = new Car();

$car->start();

echo $car->getSpeed();

这里的speedUp不是已经定义为protected了吗？怎么还能在外部调用echo $car->getSpeed();