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arrays multidimensional-array php sorting

How to Sort a Multi-dimensional Array by Value

1339

How can I sort this array by the value of the “order” key?

Even though the values are currently sequential, they will not always be.

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            How to Sort a Multi-dimensional Array by Value => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            How to Sort a Multi-dimensional Array by Value => Free
            [order] => 2
        )

    [2] => Array
        (
            [hashtag] => e7d31fc0602fb2ede144d18cdffd816b
            How to Sort a Multi-dimensional Array by Value => Ready
            [order] => 1
        )
)

2

2013

Try a usort. If you are still on PHP 5.2 or earlier, you’ll have to define a sorting function first:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero – best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() – see comparison of array sorting functions in the manual.

1

  • If you need fallback/tiebreaker sorting without any function calls to prepare values, then declare an array of rules on both sides of a single spaceship operator. 1 2 If subsequent sorting rules incorporate functional overhead, then use the ?: (ternary operator) between subsequent spaceship operator comparisons. 3 so that no extra functions are unnecessarily called.

    Dec 7, 2020 at 22:17


297

function aasort (&$array, $key) {
    $sorter = array();
    $ret = array();
    reset($array);
    foreach ($array as $ii => $va) {
        $sorter[$ii] = $va[$key];
    }
    asort($sorter);
    foreach ($sorter as $ii => $va) {
        $ret[$ii] = $array[$ii];
    }
    $array = $ret;
}

aasort($your_array, "order");

3

  • 7

    This answer is missing its educational explanation.

    Dec 7, 2020 at 21:32

  • A loop, then a native sort, then another loop? Certainly not the most elegant or performant snippet on the page.

    Dec 7, 2020 at 22:03


  • An explanation would be in order.

    Jun 6, 2021 at 22:34

294

I use this function:

function array_sort_by_column(&$arr, $col, $dir = SORT_ASC) {
    $sort_col = array();
    foreach ($arr as $key => $row) {
        $sort_col[$key] = $row[$col];
    }

    array_multisort($sort_col, $dir, $arr);
}

array_sort_by_column($array, 'order');

Edit
This answer is at least ten years old, and there are likely better solutions now, but I am adding some extra info as requested in a couple of comments.

It works because array_multisort() can sort multiple arrays. Example input:

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            How to Sort a Multi-dimensional Array by Value => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            How to Sort a Multi-dimensional Array by Value => Free
            [order] => 2
        )

First $sort_col is made which is an two dimensional array with the values being what we want to sort by and the keys matching the input array. For example for this input, choosing key $sort_col "order" we get:

Array
(
    [0] => 3,
    [1] => 2
)

array_multisort() then sorts that array (resulting in key order 1, 0) but this is only the two dimensional array. So the original input array is also passed as the $rest argument. As the keys match it will be sorted so its keys are also in the same order, giving the desired result.

Note:

  • it is passed by reference so that the supplied array is modified in place.
  • array_multisort() can sort multiple additional array like this, not just one

1

  • An explanation would be in order. E.g., what is the idea/gist? What are the tradeoffs compared to other solutions? What are the performance characteristics, both theoretical and actual examples performance measurements? For instance, is this solution dog slow or not?

    Jun 6, 2021 at 22:36