Modify array keys of an associative array

Question

I have this array

 $the_posted = Array
            (
    0 => Array
        (
            0 => 1,
            1 => 2,
            2 => 3,
            3 => 4,
        ),

    1 => Array
        (
            0 => 5,
            1 => 6,
            2 => 7,
            3 => 8,
        )

);

whose keys i need to modify.I trying to modify the array keys like

$all_array_keys = array_keys($the_posted);

 foreach ( array_keys($the_posted) as $k=>$v )
{
  $all_array_keys[$k]= rand();
}

  echo '<pre>';
  print_r($all_array_keys);
  echo "<hr/>";
  print_r($the_posted);
  echo '<pre>';

I get this result

Array
(
    [0] => 25642
    [1] => 8731
)

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
        )

    [1] => Array
        (
            [0] => 5
            [1] => 6
            [2] => 7
            [3] => 8
        )

)

The change in keys is not reflected in the final array.How do i make this work?.

possible duplicate of [In PHP, how do you change the key of an array element?](http://stackoverflow.com/questions/240660/in-php-how-do-you-change-the-key-of-an-array-element), [PHP Change Array Keys](http://stackoverflow.com/questions/308703/php-change-array-keys). — rid, Sep 10 '13 at 08:33
@rid: sorry but you are wrong. It is possible to change a key of an item. Please refer to my message below. — Scalpweb, Sep 10 '13 at 08:37
I agree that it's not clean, but the final result is exactly what this guy is trying to do, I think... — Scalpweb, Sep 10 '13 at 08:40
@rid: depends of the situation. Let's say you have a very large array, and only want to change a few keys. Building a completely new array would probably be more time consuming. That's probably a good thing to know how to use both solution. (and I actually do not care about downvote, I'm just trying to help ^^) — Scalpweb, Sep 10 '13 at 08:42

Nishu Tayal · Accepted Answer · 2013-09-10T08:52:59.570

1

You can use following code :

foreach ( array_keys($the_posted) as $k=>$v )
{   
  $new_key = rand();
  $new_posted[$new_key] = $the_posted[$v];
  unset($the_posted[$v])
}

Here, we have created a new array $new_posted which will have data with new keys like this :

Array
(
    [28228] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
        )

    [23341] => Array
        (
            [0] => 5
            [1] => 6
            [2] => 7
            [3] => 8
        )

)

edited Sep 10 '13 at 08:52

answered Sep 10 '13 at 08:47

Nishu Tayal

20,106
8
49
101

And, if and only if you're memory constrained (maybe you don't have a lot of allocated memory for PHP and the array is very big), you can also `unset($the_posted[$k])` at each iteration, which would keep the same memory footprint, at the expense of performance. But if memory is not a concern, it should be significantly faster without the `unset()`. – rid Sep 10 '13 at 08:50
@rid : agreed with you. – Nishu Tayal Sep 10 '13 at 08:51

score -1 · Answer 2 · answered Sep 10 '13 at 08:36

-1

To change the key of an item, do something like this:

$the_posted[$newkey] = $the_posted[$oldkey];
unset($the_posted[$oldkey]);

So in your case:

foreach ( $the_posted as $k=>$v )
{
    $newkey = rand();
    while(isset($the_posted[$newkey]))
       $newkey = rand();
    $the_posted[$newkey] = $the_posted[$k];
    unset($the_posted[$k]);
}

answered Sep 10 '13 at 08:36

Scalpweb

1,971
1
12
14

True. I updated the code to fix the issue. – Scalpweb Sep 10 '13 at 08:38

Modify array keys of an associative array

2 Answers2