在PHP为什么不工作

Question

class GrandClass { 
    public $data; 
    public function __construct() { 
     $this->someMethodInTheParentClass(); 
    } 
    public function someMethodInTheParentClass() { 
     $this->$data = 123456; 
    } 
} 

class MyParent extends GrandClass{ 
    public function __construct() { 
     parent::__construct(); 
    } 
} 

class Child extends MyParent { 
    // public $data; 
    public function __construct() { 
     parent::__construct(); 
    } 
    public function getData() { 
     return $this->data; 
    } 
} 

$a = new Child(); 
var_dump($a->getData()); 

PHP公告：未定义的变量：在d数据：\ test.php的第7行

PHP致命错误：在d无法访问空属性：\ test.php的第7行

Answer 1

更新您的功能someMethodInTheParentClass低于使用$这 - >数据= 123456;

public function someMethodInTheParentClass() { 
     $this->data = 123456; 
    } 

Answer 2

Use `$this->data = 123456; `instead of` $this->$data = 123456;` in below function 

public function someMethodInTheParentClass() { 
     $this->data = 123456; 
} 

Answer 3

MyParent和Child类中的构造方法是不必要的。