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PHP: re order associative array

Posted by: admin July 12, 2020 Leave a comment

Questions:

In php, I would like to have the ability to re-order an associative array by moving elements to certain positions in the array. Not necessary a sort, just a re-ordering of my choosing.

As an example, say i have an associative array as follows:

array(
 'a' => 'Element A',
 'b' => 'Element B',
 'c' => 'Element C',
);

and in one case i may want to move C before B and have the following result:

array(
 'a' => 'Element A',
 'c' => 'Element C',
 'b' => 'Element B',
);

or in another case i may want to move C before A and have the following result:

array(
 'c' => 'Element C',
 'a' => 'Element A',
 'b' => 'Element B',
);

What i am trying to show, is simply a method for saying “Hey, i want to move this array element before this other array element” or “Hey, id like to move this array element to make sure that it comes after this other array element’

Hopefully this makes sense!

Thank you to anyone in advance who cares to help me with this

How to&Answers:

If you mean to swap two values you could make a function like this:

function array_swap($key1, $key2, $array) {
        $newArray = array ();
        foreach ($array as $key => $value) {
            if ($key == $key1) {
                $newArray[$key2] = $array[$key2];
            } elseif ($key == $key2) {
                $newArray[$key1] = $array[$key1];
            } else {
                $newArray[$key] = $value;
            }
        }
        return $newArray;
    }

Answer:

For a custom sorting, you can for example create an array that is the desired order of the keys and then associate the values with them. Example:

$input = array("a"=>"Element A","b"=>"Element B","c"=>"Element C");
$order = array("c","a","b");
$out = array();
foreach($order as $k) {
    $out[$k] = $input[$k];
}

The elements in $out will be in the order specified.

Answer:

$arr = array(
  'a' => 1,
  'b' => 2,
  'move me' => 9,
  'c' => 3,
  'd' => 4,
);

Hey, I want to move [‘move me’] before [‘b’]. I can do it with only 4 lines of code!

$i = 0; foreach($arr as &$val) $val = array('sort' => (++$i * 10), 'val' => $val);
$arr['move me']['sort'] = $arr['b']['sort'] - 5;
uasort($arr, function($a, $b) { return $a['sort'] > $b['sort']; });
foreach($arr as &$val) $val = $val['val'];


I made a function for easy use:

function move_item(&$ref_arr, $key1, $move, $key2 = null)
{
  $arr = $ref_arr;
  if($key2 == null) $key2 = $key1;
  if(!isset($arr[$key1]) || !isset($arr[$key2])) return false;

  $i = 0; foreach($arr as &$val) $val = array('sort' => (++$i * 10), 'val' => $val);

  if(is_numeric($move))
  {
    if($move == 0 && $key1 == $key2) return true;
    elseif($move == 0) { $tmp = $arr[$key1]['sort']; $arr[$key1]['sort'] = $arr[$key2]['sort']; $arr[$key2]['sort'] = $tmp; }
    else $arr[$key1]['sort'] = $arr[$key2]['sort'] + ($move * 10 + ($key1 == $key2 ? ($move < 0 ? -5 : 5) : 0));
  }
  else
  {
    switch($move)
    {
      case 'up':     $arr[$key1]['sort'] = $arr[$key2]['sort'] - ($key1 == $key2 ? 15 : 5); break;
      case 'down':   $arr[$key1]['sort'] = $arr[$key2]['sort'] + ($key1 == $key2 ? 15 : 5); break;
      case 'top':    $arr[$key1]['sort'] = 5; break;
      case 'bottom': $arr[$key1]['sort'] = $i * 10 + 5; break;
      default: return false;
    }
  }
  uasort($arr, function($a, $b) { return $a['sort'] > $b['sort']; });
  foreach($arr as &$val) $val = $val['val'];
  $ref_arr = $arr;
  return true;
}

Examples:

move_item($arr, 'move me', 'up'); //move it one up
move_item($arr, 'move me', 'down'); //move it one down
move_item($arr, 'move me', 'top'); //move it to top
move_item($arr, 'move me', 'bottom'); //move it to bottom

move_item($arr, 'move me', -1); //move it one up
move_item($arr, 'move me', 1); //move it one down
move_item($arr, 'move me', 2); //move it two down

move_item($arr, 'move me', 'up', 'b'); //move it before ['b']
move_item($arr, 'move me', -1, 'b'); //move it before ['b']
move_item($arr, 'move me', 'down', 'b'); //move it after ['b']
move_item($arr, 'move me', 1, 'b'); //move it after ['b']
move_item($arr, 'move me', 2, 'b'); //move it two positions after ['b']

//Special syntax, to swap two elements:
move_item($arr, 'a', 0, 'd'); //Swap ['a'] with ['d']

I hope this helps a lot of people, because it is an awesome function! 😀

Answer:

A lot of difficult methods here 🙂 In fact, you can exploit the preserve keys feature of array_slice().

$new_element = array('new_key' => 'value');

// if needed, find the insertion index by key
$index = array_search('key to search', array_keys($old_array));

// add element at index (note the last array_slice argument)
$new_array = array_slice($old_array, 0, $index+1, true) + $new_element + array_slice($old_array, $index+1, null, true);

Answer:

array_splice unfortunately doesn’t work with associative arrays, so here’s something a little messier:

$keys = array_keys($arr);
$values = array_values($arr);

$keyIndex = array_search($someKey, $keys);
array_splice($keys, $keyIndex, 1);
array_splice($values, $keyIndex, 1);

$insertIndex = 1;
array_splice($keys, $insertIndex, 0, array($someKey));
array_splice($values, $insertIndex, 0, array($arr[$someKey]));

$arr = array_combine($keys, $values);

Answer:

i made a function based on one answer here. it takes the array of assoc array to be sorted, plus array of keys in which it should be resorted

// $data = array of assoc array
// $newKeysOrder = array("c","a","b");
function resort_assoc_array_by_keys($data, $newKeysOrder) {
  foreach($data as $v) {
    $out = [];
    foreach($newKeysOrder as $k) {
      $out[$k] = $v[$k];
    }  
    $new[] = $out;
  }
  return $new;
}