PHP natsort Function

last modified March 13, 2025

The PHP natsort function sorts an array using a "natural order" algorithm. It maintains index association, unlike regular sorting functions.

Basic Definition

The natsort function implements a sorting algorithm that orders alphanumeric strings in the way a human being would. It's case-sensitive.

Syntax: natsort(array &$array): bool. The function sorts the array in place and returns true on success or false on failure.

Basic natsort Example

This demonstrates the difference between regular sort and natural sort.

basic_natsort.php

<?php

$files = ["img1.png", "img10.png", "img2.png", "img12.png"];

// Regular sort
sort($files);
echo "Regular sort:\n";
print_r($files);

// Natural sort
natsort($files);
echo "\nNatural sort:\n";
print_r($files);

Regular sort orders lexicographically (1, 10, 12, 2), while natural sort orders numerically (1, 2, 10, 12). The output shows the difference clearly.

Case Sensitivity in natsort

natsort is case-sensitive, which affects sorting order.

case_sensitive.php

<?php

$items = ["Apple", "apple", "Banana", "banana", "1apple", "10apple"];

natsort($items);
print_r($items);

Uppercase letters come before lowercase in ASCII, so "Apple" sorts before "apple". Numbers come before letters, so "1apple" appears first.

Mixed Alphanumeric Sorting

natsort handles mixed alphanumeric strings intelligently.

mixed_sorting.php

<?php

$versions = ["version-1.9", "version-1.10", "version-2.0", "version-1.1"];

natsort($versions);
print_r($versions);

The function correctly orders version numbers: 1.1, 1.9, 1.10, then 2.0. This demonstrates its ability to handle complex alphanumeric patterns.

Preserving Keys with natsort

Unlike sort, natsort maintains key-value association.

key_preservation.php

<?php

$data = [
    "item3" => "value3",
    "item10" => "value10",
    "item1" => "value1",
    "item20" => "value20"
];

natsort($data);
print_r($data);

The output shows the array sorted by values while keeping original keys intact. This is useful when you need to maintain the relationship between keys and values.

Sorting File Names

A practical example of sorting file names with numbered sequences.

file_sorting.php

<?php

$images = [
    "vacation_photo1.jpg",
    "vacation_photo10.jpg",
    "vacation_photo2.jpg",
    "vacation_photo20.jpg",
    "vacation_photo3.jpg"
];

natsort($images);
foreach ($images as $image) {
    echo $image . "\n";
}

This demonstrates how natsort correctly orders files with numbers, producing the sequence photo1, photo2, photo3, photo10, photo20.

Best Practices

Case Sensitivity: Use natcasesort for case-insensitive sorting.
Key Preservation: Choose natsort when you need to keep keys.
Performance: For large arrays, natural sorting is slower than regular sorting.
Mixed Data: Works best with strings containing numbers.

Source

PHP natsort Documentation

This tutorial covered the PHP natsort function with practical examples showing its usage for natural order sorting scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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