Add key/value pair in between two pairs in an array

Question

I have been looking and thinking, but can't come up with a viable solution to this problem.

I have an array with sequencial numerical keys

Example:

Array
 (
    [0] => value 0
    [1] => value 1
    [2] => value 2
    [3] => value 3
)

I need to add a new key/value pair in between two specific keys in my array.

Example:

I need to add [a] => value a between keys 1 and 2 like

Array
 (
    [0] => value 0
    [1] => value 1
    [a] => value a
    [2] => value 2
    [3] => value 3
)

What I already though of doing, but seems the long way around

slicing my array in two, add my key/value pair to the back of slice one, and recombine my 2 slices into a single array
somehow advancing each key by one after key 1 modifying my new key/value pair to [2] => value a, the add it to the back of the array, and then resort my array

Any suggestions to a quick clean way to achieve this

option 1 seems okay, slice, merge, merge, the only problem i see is when there is a collision — Kevin
– Kevin, Commented Sep 25, 2014 at 6:44
No, I will make sure to keep the key unique in my new key/value pair — Pieter Goosen
– Pieter Goosen, Commented Sep 25, 2014 at 6:53

donald123 · Accepted Answer · 2014-09-25 06:46:04Z

1

Dont know why you will do it ...

    $array = array(0=>0,1=>1,2=>2,3=>3);

    $add = array('a'=>'a');

    $before_key = 2;

    $new_array = array();

    foreach($array as $key=>$val) {
        if($key===$before_key) {
            $new_array[key($add)] = $add[key($add)];
        }
        $new_array[$key] = $val;
    }
    $array = $new_array;
    var_dump($array);

answered Sep 25, 2014 at 6:46

donald123

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1 Comment

Pieter Goosen Over a year ago

In wordpress, I have to add content between two specific paragraphs. So I have already split the content into paragraphs and have already identified where the extra content should go. It is just a matter now of adding that content :-). Will test your solution this afternoon. +1 for your solution. Thank you

Cheery · Accepted Answer · 2014-09-25 07:12:05Z

1

I assume that the original array can be associative...

$ar = array
(
    '0' => 'value 0',
    '1' => 'value 1',
    '2' => 'value 2',
    '3' => 'value 3',
);

var_dump(insertAfter($ar, '1', array('a' => 'a')));

function insertAfter($arr, $key, $piece)
{
   $keys = array_keys($arr);
   $index = array_search($key, $keys);
   if ($index !== false)
      $ar = array_merge(
            array_slice($arr, 0, $index + 1, true),
            $piece, 
            array_slice($arr, $index + 1, null, true));
   return $ar;
 }

Result:

array(5) {
  [0]=>
  string(7) "value 0"
  [1]=>
  string(7) "value 1"
  ["a"]=>
  string(1) "a"
  [2]=>
  string(7) "value 2"
  [3]=>
  string(7) "value 3"
}

ps: fixed for the keys, but if there is no need in keys preservation then

function insertAfter($arr, $key, $piece)
{
   $before = array();
   $keys = array_keys($arr);
   $index = array_search($key, $keys);
   if ($index !== false)
       $before = array_splice($arr, 0, $index + 1, $piece);
   return array_merge($before, $arr);
}

edited Sep 25, 2014 at 7:12

answered Sep 25, 2014 at 6:56

Cheery

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6 Comments

Pieter Goosen Over a year ago

Will test this afternoon. +1 for your approach

Cheery Over a year ago

It lost the key, will fix it )

Pieter Goosen Over a year ago

No, that is perfect, leave as is. This will save me actually, because I would have needed to reset the keys back to numerical value

Cheery Over a year ago

@PieterGoosen Fixed it, keys are preserved

Pieter Goosen Over a year ago

I can't unfortunately roll back your change, but you original approach was perfect. Mind rolling back your change. My idea was to reset the keys after I have inserted the new key/value pair.

|

nerdsville · Accepted Answer · 2014-09-25 06:44:01Z

0

Here is my pseudocode of my approach (this is written in python but the concept is still there)

for key, item in enumerate(array):
  if key == 2:
     thirdKey = array[key]
     array[1] = a
  if key == 3:
     fourthKey = array[key]
     array[2] = thirdKey
  if key == 4:
     array[3] = fourthKey

Kind of a long approach but I hope it helps :)

answered Sep 25, 2014 at 6:44

nerdsville

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1 Comment

Pieter Goosen Over a year ago

Ya, it is quite long. And the array is always never the same lengh, it can have 3 key/value pairs or 50

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