Recursive foreach() producing duplicate results when looping - php

Question

This class is designed to iterate over a WordPress menu structure (nested arrays/objects) to produce a finished menu. While the source of my data is WordPress, I feel this question belongs on SO instead of WP.SO because the issue is rooted more in PHP (applies to anyone attempting a recursion).
For some reason, I'm seeing duplicate results in the hierarchy. Also, I'm noticing that certain HTML elements are not closing properly. It seems like I've nested everything properly, but the result is what you see here.
To assist with debugging, I've added some * to impact the markup visually. Maybe you guys know something I don't. Fingers crossed and thanks in advance for your input!
My class
class Nav_Menu
{
public $wp_nav;
public $nested_nav;
public $recursion_depth = 0;
function __construct( $menu, $args = array() )
{
$format = new Format;
if( $menu )
{
$this->wp_nav = wp_get_nav_menu_items($menu, $args);
$this->nested_nav = $this->build_tree($this->wp_nav);
$output = $this->build_output($this->nested_nav);
$output_formatted = $format->HTML($output);
// echo $output;
echo $output_formatted;
}
}
private function build_output( $menu = array() )
{
$output = '**';
$output.= $this->recurse_menu($menu, $output);
return $output;
}
private function recurse_menu( $menu = array(), $output )
{
global $post;
if( !empty($menu) && !empty($output) )
{
$this->recursion_depth++;
// ul classes
$classes_ul = array();
$classes_ul[] = ( $this->recursion_depth > 1 ? 'sub-menu' : '' );
$classes_ul[] = 'depth-' . $this->recursion_depth;
// process list wrappers
$output.= '<ul class="' . $this->process_classes($classes_ul) . '">';
// loop through menu items
foreach( $menu as $menu_key => $menu_val )
{
// process list items
$output.= '<li>' . $menu_val->title;
// if necessary, handle children and recurse
if( !empty($menu_val->children) )
{
// recurse, and call this again
$output.= $this->recurse_menu($menu_val->children, $output);
}
// process list items
$output.= '</li>';
}
// process list wrappers
$output.= '</ul>';
}
return $output;
}
private function process_classes($classes = array())
{
if( !$classes )
{
return;
}
return trim(implode(' ', $classes));
}
private function build_tree( $elements = array(), $parent_id = 0 )
{
$branch = array();
foreach($elements as $element)
{
if ($element->menu_item_parent == $parent_id)
{
$children = $this->build_tree($elements, $element->ID);
if ($children)
{
$element->children = $children;
}
$branch[] = $element;
}
}
return $branch;
}
}
$mynav = new Nav_Menu('Test Menu');
The resulting output
****
<ul class="depth-1">
<li>
One**
<ul class="depth-1">
<li>
One
<ul class="sub-menu depth-2">
<li>
Sub One
</li>
<li>
Sub Two
</li>
<li>
Sub Three
</li>
</ul>
</li>
<li>
Two
</li>
<li>
Three**
<ul class="depth-1">
<li>
One**
<ul class="depth-1">
<li>
One
<ul class="sub-menu depth-2">
<li>
Sub One
</li>
<li>
Sub Two
</li>
<li>
Sub Three
</li>
</ul>
</li>
<li>
Two
</li>
<li>
Three
<ul class="sub-menu depth-3">
<li>
Sub One
</li>
<li>
Sub Two
</li>
</ul>
</li>
<li>
Four
</li>
</ul>
WordPress menu in the backend

Answer 1

If someone knows the reason why, I'd be willing to know, so I'll reserve choosing an answer for now. My guess is some kind of odd namespacing/scope issue for the variable $output. Who knows, I'm kinda tired right now.
The fix to get a legit structure was this...
Class
class Nav_Menu
{
public $wp_nav;
public $nested_nav;
public $recursion_depth = 0;
public $output = '';
function __construct( $menu, $args = array() )
{
$format = new Format;
if( $menu )
{
$this->wp_nav = wp_get_nav_menu_items($menu, $args);
$this->nested_nav = $this->build_tree($this->wp_nav);
$this->build_output($this->nested_nav);
$output_formatted = $format->HTML($this->output);
// echo $this->output;
echo $output_formatted;
}
}
private function build_output( $menu = array() )
{
$this->recurse_menu($menu);
}
private function recurse_menu( $menu = array() )
{
global $post;
if( !empty($menu) )
{
$this->recursion_depth++;
// ul classes
$classes_ul = array();
$classes_ul[] = ( $this->recursion_depth > 1 ? 'sub-menu' : '' );
$classes_ul[] = 'depth-' . $this->recursion_depth;
// process list wrappers
$this->output.= '<ul class="' . $this->process_classes($classes_ul) . '">';
// loop through menu items
foreach( $menu as $menu_key => $menu_val )
{
// process list items
$this->output.= '<li>';
$this->output.= $menu_val->title;
// if necessary, handle children and recurse
if( !empty($menu_val->children) )
{
// recurse, and call this again
$this->recurse_menu($menu_val->children);
}
// process list items
$this->output.= '</li>';
}
// process list wrappers
$this->output.= '</ul>';
}
}
private function process_classes($classes = array())
{
if( !$classes )
{
return;
}
return trim(implode(' ', $classes));
}
private function build_tree( $elements = array(), $parent_id = 0 )
{
$branch = array();
foreach($elements as $element)
{
if ($element->menu_item_parent == $parent_id)
{
$children = $this->build_tree($elements, $element->ID);
if ($children)
{
$element->children = $children;
}
$branch[] = $element;
}
}
return $branch;
}
}
$mynav = new Nav_Menu('Test Menu'); exit;
Resulting output
<ul class="depth-1">
<li>
One
<ul class="sub-menu depth-2">
<li>
Sub One
</li>
<li>
Sub Two
</li>
<li>
Sub Three
</li>
</ul>
</li>
<li>
Two
</li>
<li>
Three
<ul class="sub-menu depth-3">
<li>
Sub One
</li>
<li>
Sub Two
</li>
</ul>
</li>
<li>
Four
</li>
</ul>
I just created a private variable for the class, and each time I need to reference it as a storage location, I just append to it. Same as before, but no more having to pass $output down some crazy method chain.
If anyone has any other ideas that could help the community, please share!

Answer 2

Update your build_output method as below:
private function build_output( $menu = array() )
{
$output = '<ul>';
$output = $this->recurse_menu($menu, $output);
$output.= '</ul>';
return $output;
}
Update your recurse_menu method as below:
private function recurse_menu( $menu = array(), $output = '')
{
global $post;
if( !empty($menu))
{
$this->recursion_depth++;
// ul classes
$classes_ul = array();
$classes_ul[] = ( $this->recursion_depth > 1 ? 'sub-menu' : '' );
$classes_ul[] = 'depth-' . $this->recursion_depth;
// loop through menu items
foreach( $menu as $menu_key => $menu_val )
{
// if necessary, handle children and recurse
if( !empty($menu_val->children) )
{
// recurse, and call this again
$output.= '<li>'.$menu_val->title.'<ul class="' . $this->process_classes($classes_ul) . '">'.$this->recurse_menu($menu_val->children).'</ul></li>';
}
else {
$output.= '<li>'.$menu_val->title.'</li>';
}
}
}
return $output;
}
NOTE: I have tested it with more further sub-level and it is working fine.