php - 无法从子对象访问父变量

Question

我试图找出为什么 Controller 类无法访问它扩展的父类的属性。

使用 $this 检索运输方式不会输出任何内容。 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？我认为扩展父类时可以访问公共(public)/ protected 变量吗？

$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';

        }
    }
}

Answer 1

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 传递到父构造函数中(或在子构造函数中创建它)

• 您可以使用 $this-> 获取船舶信息

  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';
  
          }
      }
  }
  

进一步说明:您不需要像前几行中那样实例化父级和子级:

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

一旦子级的构造函数与父级的构造函数匹配，允许数据流动，您应该只实例化子级，通过子级的构造函数发送数据(请参阅我上面提供的代码以了解其工作原理):

$controller = new OrderLinkController($data);