PHP 5.6到PHP 5.4降级：迭代器不再工作

Question

我的网站在XAMPP中使用PHP 5.6正常运行。

foreach ($treeNodeIterator as $nodeKey => $node) {

  $currentLevel = $nodeKey->getNodeLevel();

  if ($currentLevel > $depth) {

    $depth = $currentLevel;

  }

}

然后我发现我的服务器运行的是PHP 5.4。所以现在我明白了 服务器日志文件上的以下错误消息：

[13-Sep-2015 12:33:19 America/Denver] PHP Fatal error:  Call to a member function getNodeLevel() on a non-object in treeNode.php line 82

这是TreeNodeIteratorKey类：

class TreeNode {

  protected $name;

  protected $value;

  protected $children;

  protected $customData;

  //...

}

class TreeNodeIterator implements Iterator {

  private $traversalMode;

  private $rootNode;

  private $nodesToVisit;

  private $nodesToVisitLevels;

  private $currentNodeIteratorKey;

  const TRAVERSAL_MODE_BFS = 0;

  const TRAVERSAL_MODE_DFS = 1;

  const NUM_TRAVERSAL_MODES = 2;

  public function current() {

    return $this->nodesToVisit[0];

  }

  public function key() {

    return $this->currentNodeIteratorKey;

  }


}

class TreeNodeIteratorKey {

  private $nodeIndex;

  private $nodeLevel;

  private $customData;

  //...
}