How to Sort Keys of a Multidimensional Nested Array in Reverse Order Using krsort in PHP?

gitbox 2025-09-12

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<p>Title: How to Sort Keys of a Multidimensional Nested Array in Reverse Order Using krsort in PHP?</p>
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<p>In PHP, krsort() is a commonly used array function that sorts an array in reverse order by <strong>key</strong> (from largest to smallest),</p>
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<p>while preserving the key-value relationships. This is useful for sorting data structures that need to be processed in descending order based on the keys.</p>
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<h3>1. Basic Usage of krsort</h3>
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$arr = [

"c" =&gt; 3,

"a" =&gt; 1,

"b" =&gt; 2

];

krsort($arr);

print_r($arr);

The result will be:

Array

(

[c] =&gt; 3

[b] =&gt; 2

[a] =&gt; 1

)

2. Case of Multidimensional Arrays

Suppose we have a multidimensional nested array:

$data = [

"group3" =&gt; [

    "c" =&gt; 30,

    "a" =&gt; 10,

    "b" =&gt; 20

],

"group1" =&gt; [

    "x" =&gt; 100,

    "z" =&gt; 300,

    "y" =&gt; 200

],

"group2" =&gt; [

    "foo" =&gt; "bar",

    "baz" =&gt; "qux"

];

If we only want to sort the top-level keys in reverse order:

krsort($data);

print_r($data);

The top-level keys will be sorted as group3, group2, group1.

3. Recursive Sorting of Multidimensional Arrays

If we want to sort not only the top-level keys in reverse order but also recursively sort each sub-array's keys, we need to write a recursive function:

function recursiveKrsort(array &$array) {

// First, reverse sort the current level's keys

krsort($array);

// Iterate through each item and if the value is still an array, call the function recursively

foreach ($array as &amp;$value) {

    if (is_array($value)) {

        recursiveKrsort($value);

}

// Example usage

recursiveKrsort($data);

print_r($data);

This way, all levels of the array will be sorted by keys in reverse order.

4. Summary

Using krsort() can easily sort the keys of a one-dimensional array in reverse order.

For multidimensional arrays, we can use a recursive function to process each level and perform a global key sorting in reverse order.

This approach is suitable for scenarios where data, such as configuration settings or grouped data, needs to be displayed in reverse order based on the keys.
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array_key_exists