PHP - how to flip the rows and columns of a 2D array

Question

Normally I\'d be asking how to turn something like this:

1      2        3
4      5        6
7      8        9
10    11       12

Into this:

Answer 1

Just walk the array in the correct order. Assuming you have relatively small arrays, the easiest solution is just to create a brand new array during that walk.

A solution will be of the form:

$rows = count($arr);
$cols = count($arr[0]); // assumes non empty matrix
$ridx = 0;
$cidx = 0;

$out = array();

foreach($arr as $rowidx => $row){
    foreach($row as $colidx => $val){
        $out[$ridx][$cidx] = $val;
        $ridx++;
        if($ridx >= $rows){
            $cidx++;
            $ridx = 0;
        }
    }
}