How Can I Sort a Multi-Dimensional Array in PHP Using `usort()` and `uasort()`?

Sorting a Multi-Dimensional Array by Value

Many situations arise when the need to sort a multi-dimensional array is necessary. This can be achieved with the use of a user-defined comparison function within the usort() function.

Sorting by a Single Key Using usort()

To sort the given array by the value of the "order" key, we can define a sorting function as follows:

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

usort($myArray, 'sortByOrder');

Alternatively, we can 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;
});

Multi-Dimensional Sorting

This approach can be extended to sort multi-dimensional arrays. For instance, to sort by "order" and then "suborder":

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

Preserving Key Associations with uasort()

If you need to retain key associations, use uasort(). For comparison, refer to the manual's comparison of array sorting functions.

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