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;
        }
    }
}

Answer 2

Got this simple one:

$matrix = [
  [1, 2, 3],
  [1, 2, 3],
  [1, 2, 3],
];

$flipped = array_map(function($col, $i) use($matrix){
  return array_map(function($row) use($matrix, $i){
    return $row[$i];
  }, $matrix);
}, $matrix, array_keys($matrix));

Answer 3

What you need is:

function flip($array) {
    array_unshift($array, null);
    return call_user_func_array('array_map', $array);
}

Answer 4

here you go. It works. :)

$input1 = array(1,2,3);
$input2 = array(4,5,6);
$input3 = array(7,8,9);
$input4 = array(10,11,12);

$input = array($input1,$input2,$input3,$input4);

echo "\n input array";print_r($input);

// flipping matrices
$output = array();
$intern = array();

for($row=0; $row lt 4; $row++)
    for($col=0;$col lt 3;$col++)
        $intern[] = $input[$row][$col];

echo "\n intern ";print_r($intern);

// nesting the array
$count = 0;
$subcount = 0;

foreach($intern as $value)
{

    $output[$count][$subcount] = $value;
    $count++;

    if($subcount == 3)
    {
        break;
    }

    if($count == 4)
    {
        $count = 0;
        $subcount++;
    }


}


echo "\n final output ";print_r($output);

Answer 5

Modified version of the "accepted" answer, which works MUCH better IMHO:

function array2DFlip($arr) {
 if(!is_array($arr) || count($arr) < 1 || !isset($arr[0])) return array();

 $out = array();

 foreach($arr as $row_id => $row){
    foreach($row as $col_id => $val){
        $out[$col_id][$row_id] = $val;
    }
 }

 return $out;
}

Answer 6

function flip_row_col_array($array) {
    $out = array();
    foreach ($array as  $rowkey => $row) {
        foreach($row as $colkey => $col){
            $out[$colkey][$rowkey]=$col;
        }
    }
    return $out;
}