How to efficiently build a tree from a flat structure in php?

Question

array data structure:

 id   name    parent_id   children

now I have a root array, and a set of array of children, I want to build a tree structure, and this is what I have:

Updated::

function buildTree($root,$children)
{   
    foreach($children as $key=>$val){
        print_r($val);
        $val['children']=array();
        if($val['parent_id']==$root['id']){
            $root['children'][]=$val;
            //remove it so we don't need to go through again
            unset($children[$key]);
        }
    }
    if(count($root['children'])==0)return;
    foreach($root['children'] as $child){
        $this->buildTree($child,$children);
    }
}

this returns the same root,,not children added could anybody helps me with this. thanks a lot.

update: print_r($val) print out:

 Array
(
[id] => 3
[name] => parent directory2
[type] => d
[creat_time] => 2011-07-08 06:38:36
[parent_id] => 1
[user_id] => 1
)
Array
(
[id] => 5
[name] => parent directory3
[type] => d
[creat_time] => 2011-07-08 06:38:36
[parent_id] => 1
[user_id] => 1
)
 .....

ooo...because using foreach, I don't know how to unset...I am just a beginner..:) — bingjie2680, Jul 11 '11 at 06:43
@bingjie2680, you can use `foreach($arr as $key=>$val)` and then `unset($arr[$key])` — k102, Jul 11 '11 at 06:45
it seems to swipe the error away. but the whole function returns the same root, no children — bingjie2680, Jul 11 '11 at 06:50
do u have all the item available to an array, or somewhere else. I can help u with a linear time algorithm ;) — Kowser, Jul 11 '11 at 06:51
@k102,, the $children is not empty...I tried to print_r($val), I get all the children printed out. — bingjie2680, Jul 11 '11 at 06:56

score 2 · Accepted Answer · answered Jul 11 '11 at 07:01

Try to change you function to take the parameters by reference like so:

function buildTree(&$root,&$children) {

otherwise you'll get a fresh copy of your root/children arrays in each call and therefore you'll never get the whole tree.

You'll find more information at the manual: http://www.php.net/manual/en/language.references.pass.php

score 0 · Answer 2 · answered Jul 11 '11 at 06:43

0

looks like your $children array begins with 1, but your "for" begins with 0

answered Jul 11 '11 at 06:43

Greenisha

1,417
10
14

can you `var_dump($children)` and post it here? – k102 Jul 11 '11 at 06:46

score -1 · Answer 3 · edited May 23 '17 at 12:07

-1

If efficiency is what you're asking for, you might want to consider using reference instead of recursion, as explained here: https://stackoverflow.com/a/34087813/2435335

This reduces hours of execution time to less than a second

edited May 23 '17 at 12:07

Community

1
1

answered Dec 04 '15 at 11:58

ntt

426
1
4
9

How to efficiently build a tree from a flat structure in php?

3 Answers3