在PHP爲什麼不工作

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：未定義的變量：在d數據：\ test.php的第7行

PHP致命錯誤：在d無法訪問空屬性：\ test.php的第7行

Answer 1

更新您的功能someMethodInTheParentClass低於使用$這 - >數據= 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類中的構造方法是不必要的。