PHP merge multiple arrays in order of their value index

Question

I've found a lot of information on joining arrays together using array_merge, but I'm wondering how easy it is to merge multiple arrays in order of their value index, rather than simply joining them together.

For example, if we had the following three arrays:

$a = array('One','Two','Three','Four');
$b = array(1,2,3,4);
$c = array('i','ii','iii','iv');

Could we merge them into?:

One,1,i,Two,2,ii,Three,3,iii,Four,4,iv

Instead of:

One, Two, Three, Four, 1, 2, 3, 4, i, ii, iii, iv

I don't think there's a built-in function for this, just write a `for` loop. — Barmar, Jun 30 '13 at 02:43
what is the purpose? You are going to have to make your own custom merge function — Kris, Jun 30 '13 at 02:44

score 2 · Accepted Answer · answered Jun 30 '13 at 02:56

2

you can write your custom function like this.

$a = array('One','Two','Three','Four');
$b = array(1,2,3,4);
$c = array('i','ii','iii','iv');

$count = max(count($a), count($b), count($c));
$newarray = array();

for($i=0; $i < $count; $i++) {
   if (isset($a[$i])) $newarray[] = $a[$i];
   if (isset($b[$i])) $newarray[] = $b[$i];
   if (isset($c[$i])) $newarray[] = $c[$i];
}

var_dump($newarray);

answered Jun 30 '13 at 02:56

DevZer0

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This assumes all the arrays are the same length. Better to do `$count = max(count($a), count($b), count($c));` and then do an `isset()` on each array before attempting to add an index to `$newarray` – Steven Moseley Jun 30 '13 at 02:59
Thanks, this does the trick quite nicely. The arrays will always be identical in length in my application :) – James Mathieson Jun 30 '13 at 03:18

score 2 · Answer 2 · edited May 23 '17 at 12:01

I wouldn't actually use this code due to readability, but it's cool that it works.

Make an array of arrays first

$a = array('One','Two','Three','Four');
$b = array(1,2,3,4);
$c = array('i','ii','iii','iv');
$arrays = [$a, $b, $c];

then

array_unshift($arrays, null);
$n = call_user_func_array('array_merge', call_user_func_array('array_map', $arrays));
print_r($n);

yields

Array
(
    [0] => One
    [1] => 1
    [2] => i
    [3] => Two
    [4] => 2
    [5] => ii
    [6] => Three
    [7] => 3
    [8] => iii
    [9] => Four
    [10] => 4
    [11] => iv
)

demo http://codepad.org/FdZKffPQ

it makes use of this matrix transpose method https://stackoverflow.com/a/3423692

PHP merge multiple arrays in order of their value index

2 Answers2

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