Sort arrays by multi-level key values ​​in PHP, keeping key names

In PHP, the usort() function is used to sort arrays by multi-level key values. With a user-defined comparison function, it can be sorted according to key-value pairs while keeping the key names unchanged. Practical application: To sort blog comments by the number of likes, you can use usort() and the comparison function to sort in descending order by likes.

Sort arrays by multi-level key values ​​in PHP

In PHP, sort arrays by multi-level key values Can make data processing more convenient. This tutorial shows how to sort an array by multi-level key-value pairs while keeping the key names unchanged.

Using the usort()

##usort() function sorts an array using a user-defined comparison function. We can use this function to sort the array by specified key-value pairs while maintaining the key names.

<?php

function compare($a, $b) {
    return $a['key'] <=> $b['key'];
}

$data = [
    'data1' => ['key' => 10],
    'data2' => ['key' => 5],
    'data3' => ['key' => 15],
];

usort($data, 'compare');

print_r($data);
?>

Array
(
    [data2] => Array
        (
            [key] => 5
        )

    [data1] => Array
        (
            [key] => 10
        )

    [data3] => Array
        (
            [key] => 15
        )

)

compare(), which converts the key of the array elements values ​​are compared. We then use the usort() function to sort the array by key value.

Practical Case

usort() function to sort the comments of a blog post by the number of likes.

<?php

$comments = [
    1 => ['content' => '评论 1', 'likes' => 10],
    2 => ['content' => '评论 2', 'likes' => 5],
    3 => ['content' => '评论 3', 'likes' => 15],
];

function compareComments($a, $b) {
    return $b['likes'] <=> $a['likes'];
}

usort($comments, 'compareComments');

foreach ($comments as $id => $comment) {
    echo "评论 $id: {$comment['content']}, 点赞数: {$comment['likes']}<br>";
}
?>

评论 3: 评论 3, 点赞数: 15<br>
评论 1: 评论 1, 点赞数: 10<br>
评论 2: 评论 2, 点赞数: 5<br>

compareComments() function to sort the comments array by likes value (descending order) . We then iterate over the sorted array and display the content and number of likes for each comment.

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