OOP面向对象基础-封装性

class Car
{
    private $name;
    public function show(){
        echo "this is a ".$this->name;
    }
    public function __set($key,$value){
        $this->$key = $value;
    }
}

$bm = new Car;
$bm -> name ="宝马";//如果不定义__set方法,会报错  
$bm -> show();

public function __get($key)
    {
      echo  $this ->$key;
    }

$bm->name;    

public function __isset($key)
    {
       echo $this->$key;
        echo "存在";
    }
    public function __unset($key)
    {
        echo $this->$key;
        echo "我是删除";
    }

//外部不存在,内部存在
if(isset($a -> b)){
    echo "存在";
}else{
    echo "不存在";
}