Building a Parent/Child Category Structure

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Average Score	8.3
Scores Submitted	3
Date Added	Aug 20, 2004
Last Updated	Mar 19, 2007
Tags	category datafeed mysql parentchild tree

Introduction

This generates two structures: a tree and a list of objects. Both are generated from the following standard parent/child database format:

- cat_id: primary key, auto_increment
- cat_title: name of category
- cat_parent_id: points to the cat_id of this items parent.

These are two recursive functions that first build a tree structure. The second recursive function builds a sortable list of objects with their full category path as shown below:
For Cat3: Cat1 > Cat2 > Cat3

It's helpful to use a print_r on both objects to get a visual idea of what you've built.

Important Notes:
- This code will not work without a query and a database.
- The parent category needs to be included in the dataset and $directory_id needs to match it's cat_id.

Grab the Code

/************************************************************/
// Category Item class

class category_item
{
    var $cat_id;
    var $depth;
    var $cat_title;
    var $cat_parent_id;
    var $cat_long_title;

function category_item($cat_id, $depth, $cat_title, $cat_parent_id, $cat_long_title = '')
    {
        $this->cat_id = $cat_id;
        $this->depth = $depth;
        $this->cat_title = $cat_title;
        $this->cat_parent_id = $cat_parent_id;
        $this->cat_long_title = $cat_long_title;
    }
}

/*************************************************************/
// Builds the category list for the category select

$list = array();

function build_list($cat_array, $item = '', $depth = 0)
{
    global $template;
    global $list;

foreach($cat_array as $category)
    {
        $loop_item = "$item$category[cat_title]";

$category_item = new category_item($category[cat_id], $depth, $category[cat_title], $category[cat_parent_id], $loop_item);
        $list[] = $category_item;

if(count($category[children]) > 0)
        {
            $depth++;
            build_list($category[children], $loop_item." > ", $depth);
            $depth--;
        }

$loop_item = '';
    }

return $list;
}

/*************************************************************/
// Adds the object to the children array of the object with 
// a cat_id equal to $parent_id

function tree_add($tree, $parent_id, $object, $cat_id)
{
    // Only start from the given cat_id, ignore all other roots

if($parent_id == '0' and $object[cat_id] == $cat_id)
    {
        $tree[$object[cat_id]] = $object;
        return $tree;
    }

if($tree)
    {
        foreach($tree as $key => $value)
        {
            $current = $tree[$key];

// If this is the parent, add the object to it's children array
            if($current[cat_id] == $parent_id)
            {
                $tree[$key][children][$object[cat_id]] = $object;
            }
            else
            {
                // If it's not in this level, look a level deeper on the current object.
                $tree[$key][children] = tree_add($current[children], $parent_id, $object, $cat_id);
            }
        }
    }

return $tree;
}

/*************************************************************/
// This pulls the data from the database.  This will not work without a
// database connection.  This code is compatible with the phpBB2 
// mySQL database class.
//

$query = "
    select
        *
    from
        categories
    order by
        cat_id
";

$result = $db->sql_query($query);

while($category = $db->sql_fetchrow($result))
{
    $children = array();

$category[children] = $children;

$cat_id = $category[cat_id];
    $cat_parent_id = $category[cat_parent_id];

$cat_tree = tree_add($cat_tree, $cat_parent_id, $category, $cat_id);
}

$cat_list = build_list($cat_tree);

Comments

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Pauladao

Comments: 1

PHP Snippet: Building a Parent/Child Category Structure
Posted on Mar 22, 2006 12:39 pm

Hi Hawkee! This code is very usefull, but i'm getting an error while running it:

Warning: Invalid argument supplied for foreach() in c:webanunciosadmindump.php on line 35

Dump.php is what I named the script, the line with the error is:
foreach($cat_array as $category)

I tried to do something similar to this script myself, but I was not sucessfull. If you can see this and help figuring this error out, I would appreciate very much.

Best Regards;

(Marcio)

Hawkee

Comments: 398

PHP Snippet: Building a Parent/Child Category Structure
Posted on Mar 22, 2006 4:13 pm

It seems like your $cat_tree wasn't created properly. Make sure you check the data you're pulling from mySQL to be sure it's got a cat_title, cat_id and cat_parent_id for each category in your database.

rompers

Comments: 1

PHP Snippet: Building a Parent/Child Category Structure
Posted on Mar 18, 2007 11:03 pm

hello !

as now sql code should look

sorry for my bad english

thxRompers

Hawkee

Comments: 398

PHP Snippet: Building a Parent/Child Category Structure
Posted on Mar 19, 2007 2:38 am

rompers, what are you asking?

F*U*R*B*Y*

Comments: 408

PHP Snippet: Building a Parent/Child Category Structure
Posted on Mar 20, 2007 2:15 am

can you explain what this does please :) i don't really understand what you mean parent/child category structure

Building a Parent/Child Category Structure

Introduction

Grab the Code

Comments

Hawkee

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