问使用PHP的迭代器的嵌套列表？

EN

<?php
// example navigation array
$nav = array(
    'Home' => '/home',
    'Fake' => array(
        'Double Fake' => array(
            'Nested Double Fake' => '/fake/double/nested',
            'Doubly Nested Double Fake' => '/fake/double/doubly'
        ),
        'Triple Fake' => '/fake/tripe'
    ),
    'Products' => array(
        'Product 1' => '/products/1',
        'Product 2' => '/products/2',
        'Product 3' => '/products/3',
        'Nested Product' => array(
            'Nested 1' => '/products/nested/1',
            'Nested 2' => '/products/nested/2'
        )
    ),
    'Company' => '/company',
    'Privacy Policy' => '/privacy-policy'
);

class NavBuilder extends RecursiveIteratorIterator {

    // stores the previous depth
    private $_depth = 0;

    // stores the current iteration's depth
    private $_curDepth = 0;

    // store the iterator
    protected $_it;

    /**
     * Constructor.
     *
     * @access  public
     * @param   Traversable $it
     * @param   int         $mode
     * @param   int         $flags
     */
    public function __construct(Traversable $it, $mode = RecursiveIteratorIterator::SELF_FIRST, $flags = 0)
    {
        parent::__construct($it, $mode, $flags);

        // store the caching iterator
        $this->_it = $it;
    }

    /**
     * Override the return values.
     *
     * @access  public
     */
    public function current()
    {
        // the return output string
        $output = '';

        // set the current depth
        $this->_curDepth = parent::getDepth();

        // store the difference in depths
        $diff = abs($this->_curDepth - $this->_depth);

        // get the name and url of the nav item
        $name = parent::key();
        $url = parent::current();

        // close previous nested levels
        if ($this->_curDepth < $this->_depth) {
            $output .= str_repeat('</ul></li>', $diff);
        }

        // check if we have the last nav item
        if ($this->hasNext()) {
            $output .= '<li><a href="' . $url . '">' . $name . '</a>';
        } else {
            $output .= '<li class="last"><a href="' . $url . '">' . $name . '</a>';
        }

        // either add a subnav or close the list item
        if ($this->hasChildren()) {
            $output .= '<ul>';
        } else {
            $output .= '</li>';
        }

        // cache the depth
        $this->_depth = $this->_curDepth;

        // return the output ( we could've also overridden current())
        return $output;
    }

}
?>

<?php

try {

    // generate the recursive caching iterator
    $it = new RecursiveCachingIterator(new RecursiveArrayIterator($nav));

    // build the navigation with the iterator
    $it = new NavBuilder($it, RecursiveIteratorIterator::SELF_FIRST);

    // display the resulting navigation
    echo '<ul id="nav">' . PHP_EOL;
    foreach ($it as $value) {
        echo $value . "\n";
    }
    echo '</ul>' . PHP_EOL;

} catch (Exception $e) {
    var_dump($e); die;
}
?>

function arrayToListHTML($array, $level = 0) {
    static $tab = "\t";
    if (empty($array)) return;
    $tabs = str_repeat($tab, $level * 2);
    $result = "{$tabs}<ul>\n";
    foreach ($array as $i => $node):
        $result .= "{$tabs}{$tab}<li>\n{$tabs}{$tab}{$tab}{$node['title']}\n".arrayToListHTML($node['children'], $level + 1)."{$tabs}{$tab}</li>\n";
    endforeach;
    $result .= "{$tabs}</ul>\n";
    return $result;
}

<ul>
    <li>
        NodeLvl1
    </li>
    <li>
        NodeLvl1
        <ul>
            <li>
                NodeLvl2
            </li>
            <li>
                NodeLvl2
                <ul>
                    <li>
                        NodeLvl3
                    </li>
                    <li>
                        NodeLvl3
                    </li>
                </ul>
            </li>
        </ul>
    </li>
    <li>
        NodeLvl1
    </li>
</ul>

class It extends RecursiveIteratorIterator{

  protected
    $tab    = "\t";

  public function beginChildren(){

    if(count($this->getInnerIterator()) == 0)
      return;
    echo str_repeat($this->tab, $this->getDepth())."<ul>\n";
  }

  public function endChildren(){


    if(count($this->getInnerIterator()) == 0)
      return;

    echo str_repeat($this->tab, $this->getDepth)."\n</ul>";
  }

  public function nextElement(){
    echo str_repeat($this->tab, $this->getDepth())."<li>".$this->current()."</li>\n";
  }

}

$it = new It(new RecursiveArrayIterator($nodes));
foreach($it as $key => $item)
  //echo $item;
  //it will be better to write a function inside your custom iterator class to handle iterations
?>