带有 protected 数组属性的 php 继承让我非常头疼

Question

所以我决定用 PHP 创建一些类，这样我就可以使用

、
• 和 标签动态构建菜单栏。原因是因为我想跨项目重用它。

  首先是代码块，请注意，我在代码中放入了一些调试信息，因为我实际上是一名 .NET 开发人员，而且我还不知道如何正确调试:s

  <?php
  
  // Menu Items <li><a href=\"$target\">$itemName</a></li>
  class MenuItem {
      public $order;
      public $target;
      public $itemName;
  
  function __construct($itemName="", $target="", $order=0) {
      $this->order = $order;
      $this->target = $target;
      $this->itemName = $itemName;
  }
  
  public function Build() {
      //if $target is empty or $itemName is empty then return empty string (both must be present to generate an item)
      if(strcasecmp($target,"") == 0 || strcasecmp($itemName,"") == 0) { 
          return "";
      }
      return "<li><a href=\"" . $target . "\">" . $itemName . "</a></li>";
  }
  }
  
  //<li><a>$FirstMenuItem</i>
  // Submenu Root Head Item: <li><a href=\"$(optional)Target\">$ItemName</a><ul>
  // Holds a list of MenuItems and SubmenuRootItems
  // Submenu Root End Item: </ul>
  class SubMenu extends MenuItem {
      protected $itemArray;
  
      function __construct($itemName = "", $target = "", $order = 0) {
          parent::__construct($itemName, $target, $order);
          $this->itemArray = array();
      }
  
      public function Items() {
          return $this->itemArray;
      }
  
      public function AddSubMenuItem ($subMenuItem) {
          $retval = strcasecmp( get_class ($subMenuItem), "submenu") == 0 ? self::AddItem($subMenuItem) : false;
         echo"<br>second dump<br>";
          var_dump($this->itemArray); echo "<br>";
          return $retval;
      }
  
      public function AddMenuItem ($menuItem) {
          $retval =  strcasecmp( get_class ($menuItem), "menuitem") == 0 ? self::AddItem($menuItem) : false;
          echo"<br>second dump<br>"; //debug code
          var_dump($this->itemArray); echo "<br>"; //debug code
          return $retval;
      }
  
      protected function AddItem($item) {
          $itemArray[$item->itemName] = $item;
          echo "AddItem <br />"; //ugly debug code
          var_dump($itemArray); //even more of it
          return true;
      }
  
      public function Build() {
          $buildHtml = "<li>";
          $buildHtml .= strcasecmp($target, "") == 0 ?  "<a>" : "<a href=\"" . $target . "\">";
          $buildHtml .= $itemName . "</a><ul>";
          $buildHtml .= BuildSubMenu(Items());
          $buildHtml .= "</ul></li>";
      }
  
      public function BuildSubMenu($menuItems) {
          $buildHtml = "";
          echo "for each start". var_dump($menuItems) ;
          foreach($menuItems as $menuItem) {
              echo $menuItem;
              $buildHtml .= $menuItem->Build();
          }
  
          return $buildHtml;
      }
  }
  
  // Menu Root Element <ul id=\"menu\">
  // holds a list of MenuItems and SubmenuRootItems
  // Menu Root Closing Element </ul>
  class MenuBuilder extends SubMenu {
      function __construct() {
          parent::__construct(); 
      }
  
      public function Build() {  echo "<br><br><br>". var_dump($this->itemArray); echo "<br><br><br>".var_dump(parent::$this->itemArray);echo "<br><br><br>";//ugly debug code
  
          $buildHtml = "<ul id=\"menu\">";
          $buildHtml .= parent::BuildSubMenu($this->itemArray);
          $buildHtml .= "</ul>";
  
          return $buildHtml;
      }
  }
  ?>
  

  问题是整个事情都不起作用，php显然不是.NET，但我真的不知道下面的内容怎么可能是真的。为了测试，我制作了这个小 php 页面，它对我的​​新类进行了一些调用。

  Write("Create menuBuilder...");
  $menuBuilder = new MenuBuilder();
  WriteLine("Done!");
  
  Write("Create subMenu1...");
  $subMenu1 = new SubMenu("Sub Menu 1");
  WriteLine("Done!");
  
  Write("Execute subMenu1->AddMenuItem...");
  $subMenu1->AddMenuItem(new MenuItem("Menu Item 1.1", "#1.1"));
  WriteLine("Done!");
  
  Write("Create menuItem2...");
  $menuItem2 = new MenuItem("Menu Item 2","#2");
  WriteLine("Done!");
  
  Write("Execute menuBuilder->AddSubMenuItem...");
  $menuBuilder->AddSubMenuItem($subMenu1);
  WriteLine("Done!");
  Write("Execute menuBuilder->AddMenuItem...");
  $menuBuilder->AddMenuItem($menuItem2);
  WriteLine("Done!");
  

  之后，$subMenu 和 $menuBuilder 上都会转储 Items 属性

  这些调用在浏览器中的输出让我完全困惑:

  Create menuBuilder...Done!
  Create subMenu1...Done!
  Execute subMenu1->AddMenuItem...AddItem 
  array(1) { ["Menu Item 1.1"]=> object(MenuItem)#4 (3) { ["order"]=> int(0) ["target"]=>    string(4) "#1.1" ["itemName"]=> string(13) "Menu Item 1.1" } } 
  second dump
  array(0) { } 
  Done!
  Create menuItem2...Done!
  Execute menuBuilder->AddSubMenuItem...AddItem 
  array(1) { ["Sub Menu 1"]=> object(SubMenu)#3 (4) { ["itemArray":protected]=> array(0) { } ["order"]=> int(0) ["target"]=> string(0) "" ["itemName"]=> string(10) "Sub Menu 1" } } 
  second dump
  array(0) { } 
  Done!
  Execute menuBuilder->AddMenuItem...AddItem 
  array(1) { ["Menu Item 2"]=> object(MenuItem)#4 (3) { ["order"]=> int(0) ["target"]=> string(2) "#2" ["itemName"]=> string(11) "Menu Item 2" } } 
  second dump
  array(0) { } 
  Done!
  

  因此，AddItem 函数起作用了，一个项目被添加到 $itemArray 中并成功转储。然后，当函数返回到它的调用者“AddMenuItem”并且我再次转储相同的 $itemArray 时，它是空的？我真的不明白这是如何工作的:s

Answer 1

也许您不会在 AddItem 方法中更改类 itemArray 属性？

你有这个:

protected function AddItem($item) {
    $itemArray[$item->itemName] = $item;
    echo "AddItem <br />"; //ugly debug code
    var_dump($itemArray); //even more of it
    return true;
}

试试这个:

protected function AddItem($item) {
    // $this will change the class property :)
    $this->itemArray[$item->itemName] = $item;
    echo "AddItem <br />"; //ugly debug code
    var_dump($this->itemArray); //even more of it
    return true;
}

您不会在很多地方使用 $this，例如在 MenuItem->Build 方法中:

class MenuItem {
    public $order;
    public $target;
    public $itemName;

function __construct($itemName="", $target="", $order=0) {
    $this->order = $order;
    $this->target = $target;
    $this->itemName = $itemName;
}

public function Build() {
    // The $target and $itemName variables aren't inicialized
    //if $this->target is empty or $this->itemName is empty then return empty string (both must be present to generate an item)
    if(strcasecmp($this->target,"") == 0 || strcasecmp($this->itemName,"") == 0) { 
        return "";
    }
    return "<li><a href=\"" . $this->target . "\">" . $this->itemName . "</a></li>";
}
}