How to Sort a Multi-dimensional Array by Value in PHP?

Sorting a Multi-dimensional Array by Value

In a multi-dimensional array, you may encounter the need to sort its elements based on the value of a specific key. For instance, consider the following array:

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            [title] => Flower
            [order] => 3
        )

    [1] => Array
        (
            [hashtag] => b24ce0cd392a5b0b8dedc66c25213594
            [title] => Free
            [order] => 2
        )

    [2] => Array
        (
            [hashtag] => e7d31fc0602fb2ede144d18cdffd816b
            [title] => Ready
            [order] => 1
        )
)

Sorting by the "order" Key

To sort the array by the "order" key, you can employ the usort() function. Here's a comprehensive breakdown of its usage:

PHP 5.2 or Earlier:

Define a sorting function first:

function sortByOrder($a, $b) {
    if ($a['order'] > $b['order']) {
        return 1;
    } elseif ($a['order'] < $b['order']) {
        return -1;
    }
    return 0;
}

PHP 5.3 and Later:

Use an anonymous function:

usort($myArray, function($a, $b) {
    if ($a['order'] > $b['order']) {
        return 1;
    } elseif ($a['order'] < $b['order']) {
        return -1;
    }
    return 0;
});

PHP 7:

Utilize the spaceship operator:

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

PHP 7.4:

Employ an arrow function:

usort($myArray, fn($a, $b) => $a['order'] <=> $b['order']);

Multi-dimensional Sorting:

For multi-dimensional sorting, modify the sorting function to reference subsequent sorting elements if the first element is zero. For instance:

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;
});

Key Associations

If you need to maintain key associations, use uasort() instead of usort().

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