Php Can'；无法从子对象访问父变量

我试图弄明白为什么控制器类无法访问它扩展的父类的属性

使用$this检索shipping方法不会输出任何内容。Var_dump表示它是一个字符串长度为0的数组

使用parent:：返回错误“未定义的类常量'shipinfo'”

知道我做错了什么吗？我认为当父类被扩展时可以访问公共/受保护的变量

$data = trim(file_get_contents('php://input'));  
$link = new OrderLink($data);
$controller = new OrderLinkController();

class OrderLink{

protected $shipinfo = [
'name'      => '',
'address'   => '',
'unit'      => '',
'city'      => '',
'state'     => '',
'country'   => '',
'zip'       => '',
'phone'     => '',
'email'     => '',
'method'    => ''
];

protected $items;

function __construct($postdata)
{
    $xml = simplexml_load_string($postdata);

    $xml = $xml->Order;

    $billinfo = $xml->AddressInfo[1];
    $this->shipinfo['name']     =  strval($billinfo->Name->Full);
    $this->shipinfo['address']  =  strval($billinfo->Address1);
    $this->shipinfo['unit']     =  strval($billinfo->Address2);
    $this->shipinfo['city']     =  strval($billinfo->City);
    $this->shipinfo['state']    =  strval($billinfo->State);
    $this->shipinfo['country']  =  strval($billinfo->Country);
    $this->shipinfo['zip']      =  strval($billinfo->Zip);

  }
}

class OrderLinkController extends OrderLink
{

    function __construct(){

        echo 'Shipping Method: ' . $this->shipinfo['method'];
        echo parent::shipinfo['method'];

        if ($this->shipinfo['method']    == 'Local Pickup'){
            $this->shipinfo['method']    = 'Pickup';

        }
    }
}

---

有几个小问题：

• 您需要调用父构造函数，因此您应该通过子构造函数将所需的$postdata流到父构造函数中（或者在子构造函数中创建它）
• 您可以使用$this->获取shipinfo

  class OrderLinkController extends OrderLink
  {
  
      function __construct($postdata){
  
          parent::__construct($postdata);
  
          echo 'Shipping Method: ' . $this->shipinfo['method'];
          echo $this->shipinfo['method'];
  
          if ($this->shipinfo['method']    == 'Local Pickup'){
             $this->shipinfo['method']    = 'Pickup';
  
          }
      }
  }
  

进一步注意：您不需要像在前几行中那样同时实例化父级和子级：

$link = new OrderLink($data);
$controller = new OrderLinkController();

只有在子构造函数与父构造函数匹配并允许数据流动时，才应该实例化子构造函数，并通过子构造函数发送数据（请参阅上面提供的代码了解其工作原理）：

---

我还要补充Katie的答案，除了代码本身的问题外，还有类结构的问题

您拥有的类是web应用程序的典型类，

OrderLinkController

是一个负责处理传入请求的类—获取输入数据，验证输入数据，并将执行传递给业务逻辑对象模型

在这种情况下，

OrderLink

是模型，它与控制器之间不应有父子关系。他们应该保持独立，我将以这种方式修改代码：

// it may extend some BaseController class, but not the model class
class OrderLinkController 
{

    function run() {
        // get and parse the input data
        $data = trim(file_get_contents('php://input'));  
        $xml = simplexml_load_string($data);
        $xml = $xml->Order;
        // validate the data
        if ($xml->method == 'Local Pickup'){
            $xml->method = 'Pickup';
        }
        // pass the data to the model
        $model = new OrderLink($xml);
        // save the data or do something else with it
        $model->save(); 

        echo $model->getShippingInfo();
    }
}


class OrderLink{

    // it is usually better to have explicitly defined fields
    // rather than an array
    protected $name;
    protected $address;
    protected $unit;
    protected $city;
    protected $state;
    protected $country;
    protected $zip;
    protected $phone;
    protected $email;
    protected $items;

    // model gets already parsed data
    function __construct($data)
    {
        $billinfo = $data->AddressInfo[1];
        $this->shipinfo['name']     =  strval($billinfo->Name->Full);
        $this->shipinfo['address']  =  strval($billinfo->Address1);
        $this->shipinfo['unit']     =  strval($billinfo->Address2);
        $this->shipinfo['city']     =  strval($billinfo->City);
        $this->shipinfo['state']    =  strval($billinfo->State);
        $this->shipinfo['country']  =  strval($billinfo->Country);
        $this->shipinfo['zip']      =  strval($billinfo->Zip);
    }

    public function getShippingInfo() {
        return 'Shipping Method: ' . $this->method;
    }
}

// create and run the controller
$controller = new OrderLinkController();
$controller->run();

---

您正在覆盖子类中的父类_construct（）方法。因此，如果我从子类中删除构造函数，则可以访问变量？@Query-否，您不需要删除构造函数，请参见下面的答案，我已添加了进一步的注释来详细解释此概念

// it may extend some BaseController class, but not the model class
class OrderLinkController 
{

    function run() {
        // get and parse the input data
        $data = trim(file_get_contents('php://input'));  
        $xml = simplexml_load_string($data);
        $xml = $xml->Order;
        // validate the data
        if ($xml->method == 'Local Pickup'){
            $xml->method = 'Pickup';
        }
        // pass the data to the model
        $model = new OrderLink($xml);
        // save the data or do something else with it
        $model->save(); 

        echo $model->getShippingInfo();
    }
}


class OrderLink{

    // it is usually better to have explicitly defined fields
    // rather than an array
    protected $name;
    protected $address;
    protected $unit;
    protected $city;
    protected $state;
    protected $country;
    protected $zip;
    protected $phone;
    protected $email;
    protected $items;

    // model gets already parsed data
    function __construct($data)
    {
        $billinfo = $data->AddressInfo[1];
        $this->shipinfo['name']     =  strval($billinfo->Name->Full);
        $this->shipinfo['address']  =  strval($billinfo->Address1);
        $this->shipinfo['unit']     =  strval($billinfo->Address2);
        $this->shipinfo['city']     =  strval($billinfo->City);
        $this->shipinfo['state']    =  strval($billinfo->State);
        $this->shipinfo['country']  =  strval($billinfo->Country);
        $this->shipinfo['zip']      =  strval($billinfo->Zip);
    }

    public function getShippingInfo() {
        return 'Shipping Method: ' . $this->method;
    }
}

// create and run the controller
$controller = new OrderLinkController();
$controller->run();