Nested lists using PHP's iterator?

Do you need a class iterator for this? You could do this with just a simple function...

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;
}

Which will produce this output:

<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>

This covers what you've shown us, but I'm not sure what you mean by other properties. Are there more properties in each array other than title and children?

Instead of trying to use your class like an array in foreach() consider using your class to perform the function. For instance, the following code will output correctly but the function is performed inside the class.

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
?>

First let me explain few things to you. Your array has two pattens

1. One with numeric indexes
2. One with string indexes, with title and children which has be parsed differently

I think a recursive function plays very nice role on this part, rather than complex logics. And our recursive function has to be able to handle both patterns separately.

Here is my version of the function you could use with explanation

function arraytolist(Array $array) { //ensure what you receive is array
  if(count($array)) { //only if it has some items
    //In case the array has `title` index we encountered out PATTERN 2
    if(isset($array['title'])) {
        $o = "<li>";
        $o .= $array['title']; //simply add the title
        $o .= arraytolist($array['children']); //and pass the children to this function to verify again
        $o .= "</li>";
    } else { //if its a normal array, //PATTERN 1
        $o = "<ul>";
        foreach($array as $value) {
            $n = "";
            if(is_array($value)) {  //in case its an array again, 
                //send it to this very same function so that it will return as output again
                $n .= arraytolist($value);
            } else {
                $n .= "<li>$value</li>";
            }
            $o .= strlen($n) ? $n : ""; //if $n has something use it otherwise not
        }
        $o .= "</ul>"; //lets close the ul
    }
    return $o;
  }
}

Some Advantage of this function

• No iteration level
• As long as its an array and has item, keeps on building them
• Power of simple logic in PHP

I would opt for a simple recursive function that flattens the array into the text/html format:

function arrToList( $arr, $embedded = false ) {
    $output = array();
    if ( $embedded ) $output[] = '<li>';
    $output[] = '<ul>';
    foreach ( $arr as $key => $values ) {
        $output[] = '<li>'.$values['title'].'</li>';
        if ( $values['children'] ) {
            $output[] = arrToList( $values['children'], true );
        }
    }
    $output[] = '</ul>';
    if ( $embedded ) $output[] = '</li>';
    return implode(PHP_EOL, $output);
}

Output from using your input:

• NodeLvl1
• NodeLvl1
• • NodeLvl2
  • NodeLvl2
  • • NodeLvl3
    • NodeLvl3
• NodeLvl1

or the actual code:

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

Cheers