Nested lists using PHP's iterator? - php

Question

I'm trying to display this kind of array:
$nodes = array(
1 => array(
'title' => 'NodeLvl1',
'children' => array(),
),
2 => array(
'title' => 'NodeLvl1',
'children' => array(
1 => array(
'title' => 'NodeLvl2',
'children' => array(),
),
2 => array(
'title' => 'NodeLvl2',
'children' => array(
1 => array(
'title' => 'NodeLvl3',
'children' => array(),
),
2 => array(
'title' => 'NodeLvl3',
'children' => array(),
),
),
),
),
),
3 => array(
'title' => 'NodeLvl1',
'children' => array(),
),
);
like this:
<ul>
<li>
NodeLvl1
</li>
<li>
NodeLvl1
<ul>
<li>NodeLv2</li>
...
</ul>
</li>
...
Basically a nested list taking into account the "children" property. So far I've come up with this:
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() + 1).'<li>';
}
}
$it = new It(new RecursiveArrayIterator($nodes));
foreach($it as $key => $item)
echo $item;
Which doesn't work quite right: I get each item wrapped between <ul>s and I don't know how can I close <li>s...
Any ideas on how to make this work? Also is it possible to get all the array properties (the actual element), instead of just the "title" property inside my foreach() loop? And can this be done with objects instead of arrays?

Answer 1

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?

Answer 2

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
?>

Answer 3

You can use RecursiveCachingIterator to do what you want. Here is an example, (source: https://github.com/cballou/PHP-SPL-Iterator-Interface-Examples/blob/master/recursive-caching-iterator.php)
<?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>' . $name . '';
} else {
$output .= '<li class="last">' . $name . '';
}
// either add a subnav or close the list item
if ($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;
}
}
?>
Usage
<?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;
}
?>

Answer 4

First let me explain few things to you. Your array has two pattens
One with numeric indexes
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

Answer 5

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