Inheritance and method overloading of php classes

//Use the autoloader to load classes: (short version)

spl_autoload_register(function($className){
    require './class/'.$className.'.php'; 
});

//$smartPhone = new SmartPhone('Apple','iPhone8', 5888);

/ ///There are no these three attributes in the SmartPhone class at this time, can they be output?

//echo 'Brand: '.$smartPhone->brand.'
'; //Normal :public can be accessed externally

//echo 'Model: '.$smartPhone->model.'
'; //Error: protected can only be accessed in the current class and subclasses

//echo 'Price: '.$smartPhone->price. '
';//Error: private is only accessible to the current class

* What if these attributes can be accessed normally?

* There are two options to achieve

* 1. Set all access controls of related properties in the parent class MobilePhone to public

* 2. Set the parent class MobilePhone The access control of all relevant attributes in is set to protected, and a query is created in the subclass SmartPhone

* We adopt the second option

$smartPhone = new SmartPhone('HUAWEI','P20', 5488,true,true);
//下面我们换一组数据来初始化对象,验证parent::__contrunctor()
$smartPhone = new SmartPhone('MI','MIX2', 3599,true,true);
//此时SmartPhone类中并无这三个属性,可以输出吗?
echo &#39;品牌: &#39;.$smartPhone->brand.&#39;<br>&#39;; 
echo &#39;型号: &#39;.$smartPhone->model.&#39;<br>&#39;; 
echo &#39;价格: &#39;.$smartPhone->price. &#39;<br>&#39;;
//下面输出二个在子类中扩展的属性
echo &#39;照相:&#39;.($smartPhone->camera?&#39;支持&#39;:&#39;没有&#39;).&#39;<br>&#39;;
echo &#39;上网:&#39;.($smartPhone->internet?&#39;支持&#39;:&#39;没有&#39;).&#39;<br>&#39;;
echo $smartPhone->call().&#39;<br>&#39;; //call()是父类中的方法
echo $smartPhone->game().&#39;<br>&#39;; //game()是子类中的方法

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