PHP - sort array by parent and id (advanced)

Question

I have an array of arrays - each has own id and parent id values. I want to sort it so that every child should be beneath it's parent. Let me show You my code:

Given Array:

$arr = array(array('id' => 15, 'parent' => 12), 
array('id' => 10, 'parent' => 12), 
array('id' => 12, 'parent' => 12), 
array('id' => 17, 'parent' => 12), 
array('id' => 21, 'parent' => 15), 
array('id' => 13, 'parent' => 15), 
array('id' => 15, 'parent' => 15), 
array('id' => 25, 'parent' => 15), 
array('id' => 7, 'parent' => 7), 
array('id' => 18, 'parent' => 7), 
array('id' => 4, 'parent' => 7), 
array('id' => 1, 'parent' => 3), 
array('id' => 5, 'parent' => 5), 
array('id' => 2, 'parent' => 7));

How the output should looki like (asc by parents, every children also ascending - always under parent (parent always as first)):

      0 =>
          'id' => int 1
          'parent' => int 3
      1 =>
          'id' => int 5
          'parent' => int 5
      2 =>
          'id' => int 7
          'parent' => int 7
      3 =>
          'id' => int 2
          'parent' => int 7
      4 =>
          'id' => int 4
          'parent' => int 7
      5 =>
          'id' => int 18
          'parent' => int 7
      6 =>
          'id' => int 12
          'parent' => int 12
      7 =>
          'id' => int 10
          'parent' => int 12
      8 =>
          'id' => int 15
          'parent' => int 12
      9 =>
          'id' => int 17
          'parent' => int 12
      10 =>
          'id' => int 15
          'parent' => int 15
      11 =>
          'id' => int 13
          'parent' => int 15
      12 =>
          'id' => int 21
          'parent' => int 15
      13 =>
          'id' => int 25
          'parent' => int 15

Question: I'am wondering what is the easiest solution to achieve this ? I've managed to do that, but I cant stop the feeling that there is a way to do that in quicker and more optimal way..

Here is my code:

function groupByParent ($array)
{
    $groups = array();
    foreach ($array as $a) {
        $groups[$a['parent']][] = $a;
    }
    return $groups;
}
function insideSort ($array)
{
    foreach ($array as $k => $v) {
        usort($array[$k], function($a, $b){
           return $a['id'] == $b['parent'] ? -1 : 1;
        });
        $f = array_shift($array[$k]);
        sort($array[$k]);
        array_unshift($array[$k], $f);
    }
    return $array;
}
function finalSort($array)
{
    $final = array();
    foreach ($array as $a) {
        $final = array_merge($final, $a);
    }
    return $final;
}

$grr = groupByParent($arr);
$irr = insideSort($grr);
ksort($irr);
$res = finalSort($irr);

Is there easier way to achieve it ?

Cheers

sevavietl · Accepted Answer · 2016-12-31 23:33:24Z

1

You can use array_multisort along with array_column:

array_multisort(
    array_column($arr, 'parent'),
    array_column($arr, 'id'),
    $arr
);

Here is working demo.

I guess this is the simplest and the most right way to do, as array_multisort was created for such cases.

answered Dec 31, 2016 at 23:33

sevavietl

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1 Comment

user7360969 Over a year ago

not working - parents arent always on top of their children

Moak · Accepted Answer · 2016-12-31 17:22:01Z

You want to look in to usort to sort an array by values using a user-defined comparison function

<?php
$arr = [
    ['id' => 15, 'parent' => 12],
    ['id' => 10, 'parent' => 12],
    ['id' => 12, 'parent' => 12],
    ['id' => 17, 'parent' => 12],
    ['id' => 21, 'parent' => 15],
    ['id' => 13, 'parent' => 15],
    ['id' => 15, 'parent' => 15],
    ['id' => 25, 'parent' => 15],
    ['id' => 7, 'parent' => 7],
    ['id' => 18, 'parent' => 7],
    ['id' => 4, 'parent' => 7],
    ['id' => 1, 'parent' => 3],
    ['id' => 5, 'parent' => 5],
    ['id' => 2, 'parent' => 7],
];
usort(
    $arr,
    function ($a, $b) {
        if ($a['parent'] == $b['parent']) {
            if ($a['id'] == $b['id']) {
                return 0;
            }

            return ($a['id'] < $b['id']) ? -1 : 1;
        }

        return ($a['parent'] < $b['parent']) ? -1 : 1;
    }
);
var_dump($arr);

This outputs

array(14) {
  [11]=>
  array(2) {
    ["id"]=>
    int(1)
    ["parent"]=>
    int(3)
  }
  [12]=>
  array(2) {
    ["id"]=>
    int(5)
    ["parent"]=>
    int(5)
  }
  [13]=>
  array(2) {
    ["id"]=>
    int(2)
    ["parent"]=>
    int(7)
  }
  [10]=>
  array(2) {
    ["id"]=>
    int(4)
    ["parent"]=>
    int(7)
  }
  [8]=>
  array(2) {
    ["id"]=>
    int(7)
    ["parent"]=>
    int(7)
  }
  [9]=>
  array(2) {
    ["id"]=>
    int(18)
    ["parent"]=>
    int(7)
  }
  [1]=>
  array(2) {
    ["id"]=>
    int(10)
    ["parent"]=>
    int(12)
  }
  [2]=>
  array(2) {
    ["id"]=>
    int(12)
    ["parent"]=>
    int(12)
  }
  [0]=>
  array(2) {
    ["id"]=>
    int(15)
    ["parent"]=>
    int(12)
  }
  [3]=>
  array(2) {
    ["id"]=>
    int(17)
    ["parent"]=>
    int(12)
  }
  [5]=>
  array(2) {
    ["id"]=>
    int(13)
    ["parent"]=>
    int(15)
  }
  [6]=>
  array(2) {
    ["id"]=>
    int(15)
    ["parent"]=>
    int(15)
  }
  [4]=>
  array(2) {
    ["id"]=>
    int(21)
    ["parent"]=>
    int(15)
  }
  [7]=>
  array(2) {
    ["id"]=>
    int(25)
    ["parent"]=>
    int(15)
  }
}
➜  promote-api git:(develop) ✗ php test.php
array(14) {
  [0]=>
  array(2) {
    ["id"]=>
    int(1)
    ["parent"]=>
    int(3)
  }
  [1]=>
  array(2) {
    ["id"]=>
    int(5)
    ["parent"]=>
    int(5)
  }
  [2]=>
  array(2) {
    ["id"]=>
    int(2)
    ["parent"]=>
    int(7)
  }
  [3]=>
  array(2) {
    ["id"]=>
    int(4)
    ["parent"]=>
    int(7)
  }
  [4]=>
  array(2) {
    ["id"]=>
    int(7)
    ["parent"]=>
    int(7)
  }
  [5]=>
  array(2) {
    ["id"]=>
    int(18)
    ["parent"]=>
    int(7)
  }
  [6]=>
  array(2) {
    ["id"]=>
    int(10)
    ["parent"]=>
    int(12)
  }
  [7]=>
  array(2) {
    ["id"]=>
    int(12)
    ["parent"]=>
    int(12)
  }
  [8]=>
  array(2) {
    ["id"]=>
    int(15)
    ["parent"]=>
    int(12)
  }
  [9]=>
  array(2) {
    ["id"]=>
    int(17)
    ["parent"]=>
    int(12)
  }
  [10]=>
  array(2) {
    ["id"]=>
    int(13)
    ["parent"]=>
    int(15)
  }
  [11]=>
  array(2) {
    ["id"]=>
    int(15)
    ["parent"]=>
    int(15)
  }
  [12]=>
  array(2) {
    ["id"]=>
    int(21)
    ["parent"]=>
    int(15)
  }
  [13]=>
  array(2) {
    ["id"]=>
    int(25)
    ["parent"]=>
    int(15)
  }
}

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