How can I sort multi-dimensional arrays in PHP by one or more keys?

Sorting Multi-dimensional Arrays by Value

When working with multi-dimensional arrays, it may be necessary to sort the array based on the value of a specific key. For instance, if you have an array containing a list of images, you might want to sort them by their date or size.

Sorting by a Single Key

To sort an array by a single key, you can use the usort() function. This function takes two parameters: the array to be sorted and a sorting function. The sorting function must take two parameters, which represent the two elements to be compared.

For example, let's say we have the following array, and we want to sort it by the value of the "order" key:

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
        )
)

To sort this array, we can use the following sorting function:

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

Then, we can pass this function to the usort() function:

usort($myArray, 'sortByOrder');

After sorting, the array will be ordered by the value of the "order" key:

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

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

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

Sorting by Multiple Keys

To sort an array by multiple keys, you can use the following approach:

1. Create a sorting function that compares the values of the first key.
2. If the values of the first key are equal, compare the values of the second key.
3. Continue comparing the values of subsequent keys until a difference is found.

For example, let's say we have the following array, and we want to sort it by the value of the "order" key, and then by the value of the "title" key:

Array
(
    [0] => Array
        (
            [hashtag] => a7e87329b5eab8578f4f1098a152d6f4
            [title] => Flower
            [order] => 1
        )

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

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

    [3] => Array
        (
            [hashtag] => c1ede105cf8a54bbfb9f06542a9971bb
            [title] => Ready
            [order] => 3
        )
)

To sort this array, we can use the following sorting function:

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