Using recursion to build navigation - php

Question

I'm building navigation for a site and for the life of me I can't figure out recursion. I have all my data stored via MySQL using this design:
I've read several links on how recursion works and I must be slow because it's difficult for me to grasp. I've tried to write something and I know it is not even close to what I really need, but it's a start:
PDO
public function viewCategories()
{
$viewSQL = "SELECT * FROM categories";
try
{
$pdo = new PDO('mysql:host=localhost;dbname=store','root','');
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
$categoryVIEW = $pdo->prepare($viewSQL);
$categoryVIEW->execute();
$array = $categoryVIEW->fetchAll(PDO::FETCH_ASSOC);
$categoryVIEW->closeCursor();
$json = json_encode($array);
return $json;
}
catch(PDOexception $e)
{
return $e->getMessage();
exit();
}
}
Recursion
$return = json_decode($category->viewCategories(),true);
function buildNavigation($json)
{
foreach($json as $item)
{
if($item['category_id'] === $item['parent'])
{
print('<li>'.$item['category_name'].'</li>');
if($item['category_id'] === $item['parent'])
{
print('<li>match'.$item['category_name'].'</li>');
buildNavigation($json);
}
}
}
buildNavigation($return);
as expected this will never enter the condition. I did try to figure this out on my own since this is a good thing to have knowledge of, but I guess it's beyond my mental capacity :(
Thanks for having a look :)
UPDATE
I know this has been answered already, but is there a way I can do this to build an associative array? I have been playing around with a function that ALMOST works for me that I got from HERE, but it adds an extra array that I do NOT want.
Method
private function buildCategories($array,$parent)
{
$result = array();
foreach($array as $row)
{
if($row['parent'] == $parent)
{
$result[$row['category_name']] = $this->buildCategories($array,$row['category_id']);
}
}
return $result;
}
$json = json_encode($this->buildCategories($array,NULL));
return $json;
I want this:
{"reloading":{"components","presses and dies","tumblers & scales","tools & accessories","shotshell reloading"}
but what I get is this:
{"reloading":{"components":[],"presses and dies":[],"tumblers & scales":[],"tools & accessories":[],"shotshell reloading":[]}

Answer 1

Here's an example with recursion.
function buildNavigation($items, $parent = NULL)
{
$hasChildren = false;
$outputHtml = '<ul>%s</ul>';
$childrenHtml = '';
foreach($items as $item)
{
if ($item['parent'] == $parent) {
$hasChildren = true;
$childrenHtml .= '<li>'.$item['category_name'];
$childrenHtml .= buildNavigation($items, $item['category_id']);
$childrenHtml .= '</li>';
}
}
// Without children, we do not need the <ul> tag.
if (!$hasChildren) {
$outputHtml = '';
}
// Returns the HTML
return sprintf($outputHtml, $childrenHtml);
}
print buildNavigation($items);
That script produces the following output :
<ul>
<li>Menu 1</li>
<li>Menu 2
<ul>
<li>Sub Menu 2.1</li>
<li>Sub Menu 2.2</li>
<li>Sub Menu 2.3
<ul>
<li>Sub Menu 2.2.1</li>
<li>Sub Menu 2.2.2</li>
<li>Sub Menu 2.2.3</li>
</ul>
</li>
</ul>
</li>
<li>Menu 3</li>
</ul>

Answer 2

I have the same above code with little bit modification, so that a user can apply different css on each level of menu, now its showing classes of sub menu like child-class1 when its in 1st sub menu , and it will show child-class2 when its in 2nd sub menu and so on...
<?php
function buildNavigation($items, $parent = NULL, $n=NULL)
{
$hasChildren = false;
if ($parent == NULL)
{
$level=0;
$outputHtml = '<ul class="parent-class">%s</ul>';
}
else
{
if($n==NULL)
{
$level=1;
}
else
{
$level=$n;
}
$outputHtml = '<ul class="child-class'.$level.'">%s</ul>';
}
$childrenHtml = '';
foreach($items as $item)
{
if ($item['parent'] == $parent) {
$hasChildren = true;
$childrenHtml .= '<li>'.$item['ptitle'].'';
$next = ++$level;
$childrenHtml .= buildNavigation($items, $item['pageid'],$next);
$childrenHtml .= '</li>';
}
}
// Without children, we do not need the <ul> tag.
if (!$hasChildren) {
$outputHtml = '';
}
// Returns the HTML
return sprintf($outputHtml, $childrenHtml);
}
echo buildNavigation($ppages);
?>
it will show out put like this
<ul class="parent-class">
<li>
page 1
<ul class="child-class1">
<li>
this is child page
<ul class="child-class2">
<li>
child of child </li>
</ul>
</li>
</ul>
</li>
</ul>
I would like to thanks Mr #Maxime Morin.