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

gitbox 2025-09-12

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<p>Title: How to Reverse Sort Keys in a Multidimensional Nested Array Using krsort in PHP?</p>
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<p>krsort() is a commonly used array function in PHP. It sorts an array by <strong>keys</strong> in descending order (from high to low),</p>
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<p>while maintaining the key-value relationship. This is particularly useful when working with data structures that require sorting by key in descending order.</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. For 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 reverse sort only the outermost layer’s keys:

krsort($data);

print_r($data);

The top-level keys will become group3, group2, group1.

3. Recursively Sorting Multidimensional Arrays

If we want to reverse sort the keys not only for the outermost layer, but also for every sub-array, we need to write a recursive function:

function recursiveKrsort(array &$array) {

// First, reverse sort the keys for the current layer

krsort($array);

// Traverse each element, and if the value is an array, recursively call the function

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 reverse sorted by their keys.

4. Summary

Using krsort() allows easy reverse sorting of keys in one-dimensional arrays.

For multidimensional arrays, a recursive function can be used to handle each layer and achieve global key reversal.

This method is useful for scenarios where data needs to be sorted and displayed based on keys, such as configuration or grouped data.
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krsort