Rearrange PHP Array, reorder 1, 2, 3, 4, 5, 6, 7, 8, 9 to 1, 4, 7, 2, 5, 8, 3, 6, 9-CodePudding

Here is the thing, I have an array that I'd like to reorder by every 3rd item. So it's 1st, 4th, 7th and then 2nd, 5th, 8th and 3rd, 6th, 9th.

from this:

$items = array('1','2','3','4','5','6','7','8','9');

to this:

$reordered_items = array('1','4','7','2','5','8','3','6','9');

Or it can be 3 separate arrays as well. Like this:

['1', '4', '7']
['2', '5', '8']
['3', '6', '9']

Tried array_chunk($items, count($items) / 3) but it just returns same array divided into 3 equall arrays.

['1', '2', '3']
['4', '5', '6']
['7', '8', '9']

I don't know if I should use array_chunk and then something else to achieve what I want. So let me know what are your thoughts about this.

Thanks!

CodePudding user response：

The simplest way I can think of is to loop over the list three times:

Start at element 0, skipping by 3, stop when past end of list
Start at element 1, skipping by 3, stop when past end of list
Start at element 2, skipping by 3, stop when past end of list

That can be easily achieved using C-style for loop syntax:

$maxKey = count($items) - 1;
$rearrangedItems = [];
for ( $key=0; $key<=$maxKey; $key =3 ) {
    $rearrangedItems[] = $items[$key];
}
for ( $key=1; $key<=$maxKey; $key =3 ) {
    $rearrangedItems[] = $items[$key];
}
for ( $key=2; $key<=$maxKey; $key =3 ) {
    $rearrangedItems[] = $items[$key];
}

If you needed to generalize to different offsets, you could put the whole thing into an outer loop rather than copying and pasting:

$offset = 3;
$maxKey = count($items) - 1;
$rearrangedItems = [];
for ( $start=0; $start<$offset; $start   ) {
    for ( $key=$start; $key<=$maxKey; $key =$offset ) {
        $rearrangedItems[] = $items[$key];
    }
}

CodePudding user response：

Try this

$items = array('1','2','3','4','5','6','7','8','9');
$tmp = [];
for ($i = 0; $i < count($items); $i  ) {
    $tmp[$i%3][] = $items[$i];
}
$result = array_merge($tmp[0], $tmp[1], $tmp[2]);
print_r($result);