Converting a One-Dimensional Array into a Nested Array Using Relationship Keys

Question

Say I have an array with keys representing id and values representing parent:

4  => 0
2  => 0
5  => 2
6  => 5
8  => 0
9  => 0
10 => 8
12 => 0
13 => 0
14 => 0
18 => 7
19 => 18
20 => 19
21 => 20
22 => 21
23 => 22
24 => 23
28 => 20
7  => 5

You could also read this as an object:

  { 
   id     : 4,
   parent : 0
  } // etc...

The multidimensional array I'd want to achieve from this would be:

How would I go about doing this?

Seems like Graph (in Computer Science)?

Alvin Wong
– Alvin Wong

2012-07-20 09:30:11 +00:00
Commented Jul 20, 2012 at 9:30 — Alvin Wong
– Alvin Wong, Commented Jul 20, 2012 at 9:30
certainly smells like homework

Pete
– Pete

2012-07-20 09:31:59 +00:00
Commented Jul 20, 2012 at 9:31 — Pete
– Pete, Commented Jul 20, 2012 at 9:31
it looks "weight" in an sorted array

Gntem
– Gntem

2012-07-20 09:34:14 +00:00
Commented Jul 20, 2012 at 9:34 — Gntem
– Gntem, Commented Jul 20, 2012 at 9:34

Community · Accepted Answer · 2017-05-23 12:13:17Z

3

If you write a little helper function to rework your data to a structure similar to:

$input = array(
  array('id' => '4', 'parent' => '0'),
  // ...
);

which could be achieved with something like:

$data = array_map(function ($entry) {
  list($id, $parent) = array_map('trim', explode('=>', $entry));
  return array(
    'id' => $id,
    'parent' => $parent
  );
}, explode("\n", $data));

you could then use a function I used in a similar question:

function flatToNested($d, $r = 0, $p = 'parent', $k = 'id', $c = 'children') {
  $m = array();
  foreach ($d as $e) {
    isset($m[$e[$p]]) ?: $m[$e[$p]] = array();
    isset($m[$e[$k]]) ?: $m[$e[$k]] = array();
    $m[$e[$p]][] = array_merge($e, array($c => &$m[$e[$k]]));
  }
  return $m[$r];
}

to produce a nested array with:

$nested = flatToNested($data);

demo: http://codepad.viper-7.com/HAZxaA

edited May 23, 2017 at 12:13

CommunityBot

11 silver badge

answered Jul 20, 2012 at 9:42

Yoshi

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3 Comments

pat34515 Over a year ago

What if the values are strings, i.e. id=>'node-4',parent='node-0', instead of id=4 etc..? How could I modify this function?

Yoshi Over a year ago

@Patrick I don't think that this should be a problem, as long as they are unique flatToNested would handle it correctly.

Yoshi Over a year ago

@Patrick try: $nested = flatToNested($doesntwork, 'node0'); The $r paramater to flatToNested selects the root node to return.

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