retain order of one element but shuffle another in php array?

Question

Consider a m-dimensional php array that looks like this:

print_r($arr)

Array (
[0] => Array ( [stimid] => 6 [list] => L01 ) 
[1] => Array ( [stimid] => 3 [list] => L01 ) 
[2] => Array ( [stimid] => 2 [list] => L02 ) 
[3] => Array ( [stimid] => 5 [list] => L02 )
[4] => Array ( [stimid] => 1 [list] => L03 )
[5] => Array ( [stimid] => 4 [list] => L03 )
)

Notice that the 'stimid' element is in random order but the 'list' element is ascending. I'm simply after a shuffle of this array such that the 'list' elements remain contiguous. What I'd like the order of the new array to be, for example, is:

print_r($new_arr)

Array (
[0] => Array ( [stimid] => 1 [list] => L03 ) 
[1] => Array ( [stimid] => 4 [list] => L03 ) 
[2] => Array ( [stimid] => 3 [list] => L01 ) 
[3] => Array ( [stimid] => 6 [list] => L01 )
[4] => Array ( [stimid] => 2 [list] => L02 )
[5] => Array ( [stimid] => 5 [list] => L02 )
)

Also notice that the order of the rows within each 'list' type need not retain their order.

This may be a very simple problem, but I can't seem to solve it! Any help is appreciated.

is there a common convention that would allow for this process to be automated? I'm not really seeing pattern that would allow for a generic function per se... — thescientist
– thescientist, Commented Jul 8, 2011 at 0:10

Glass Robot · Accepted Answer · 2011-07-08 00:40:12Z

Not pretty or efficient but:

$input = Array (
0 => Array ( 'stimid' => 6, 'list' => L01 ), 
1 => Array ( 'stimid' => 3, 'list' => L01 ), 
2 => Array ( 'stimid' => 2, 'list' => L02 ), 
3 => Array ( 'stimid' => 5, 'list' => L02 ),
4 => Array ( 'stimid' => 1, 'list' => L03 ),
5 => Array ( 'stimid' => 4, 'list' => L03 ),
);


shuffle($input);
$list = array();

foreach ($input as $pos => $item)
{
    $list[ $item['list'] ][] = $item;
}

$out = array();

foreach ($list as $item)
{
    $out = array_merge($item, $out);
}

print_r($out);

Output:

Array
(
    [0] => Array
        (
            [stimid] => 1
            [list] => L03
        )

    [1] => Array
        (
            [stimid] => 4
            [list] => L03
        )

    [2] => Array
        (
            [stimid] => 5
            [list] => L02
        )

    [3] => Array
        (
            [stimid] => 2
            [list] => L02
        )

    [4] => Array
        (
            [stimid] => 3
            [list] => L01
        )

    [5] => Array
        (
            [stimid] => 6
            [list] => L01
        )

)

Hans Kerkhof · Accepted Answer · 2011-07-08 00:36:00Z

0

You can do it like this:

$new_arr = deep_shuffle_array($arr);
print_r($new_arr);

function deep_shuffle_array(array $array){
    foreach($array as $k => $v){
        shuffle($v);
        $new_array[$k] = $v;
    }
    return $new_array;
}

Works for nested array's on 1 level deep.

answered Jul 8, 2011 at 0:36

Hans Kerkhof

4423 silver badges7 bronze badges

1 Comment

Mark Tomlin Over a year ago

Then wrap it around a recursive function to make it work on n-depth arrays.

Dennis Crane · Accepted Answer · 2011-07-08 00:37:21Z

0

function cmp($a, $b) {
    if ($a['stimid'] == $b['stimid']) {
        return 0;
    }
    return ($a['stimid'] < $b['stimid']) ? -1 : 1;
}

uasort($array, 'cmp');

answered Jul 8, 2011 at 0:37

Dennis Crane

4612 silver badges7 bronze badges

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