phparrayssortingdecimalnatural-sort

Natural sort an array of strings with optional leading decimal values


I want to sort an array with numbers in natural order, so numbers with a bigger value come after smaller ones like this:

$numbers = array('10 Apple', '2 Grapes', '3 Apples', '3.2 Apples', '3.1 Apples', '3.3 Apples', '3.10 Apples', '3.11 Apples', 'Lots of Apples');
natsort($numbers);

This is what I get as result, which is not the result I need, decimals are not threated correctly.

print_r($numbers);
Array
(
    [1] => 2 Grapes
    [2] => 3 Apples
    [4] => 3.1 Apples
    [3] => 3.2 Apples
    [5] => 3.3 Apples
    [6] => 3.10 Apples
    [7] => 3.11 Apples
    [0] => 10 Apple
    [8] => Lots of Apples
)

There is already a similar question Array Sorting in php for decimal values but no fitting answer was found there.

The expected output for a property sorting would be

Array
(
    [1] => 2 Grapes
    [2] => 3 Apples
    [4] => 3.1 Apples
    [6] => 3.10 Apples
    [7] => 3.11 Apples
    [3] => 3.2 Apples
    [5] => 3.3 Apples
    [0] => 10 Apple
    [8] => Lots of Apples
)

So I would kind of expect natsort() do to exactly that, but it looks like it is buggy and I have to implement a similar logic by my self? Is that correct?

One solution I am thinking of is to reformat the numbers somehow to fixed precision and hope that natsort() works then, but I am wondering if there are easier solutions or PHP-builtin ones.

I tried https://github.com/awssat/numbered-string-order which is very interesting but also does not support decimals.


Solution

  • I'm not 100% sure of your specification so please test this, but strnatcmp seems like it can be used to run a natsort variant in usort. If both strings passed to the comparator start with float numbers, then cast them to floats and use the spaceship, otherwise, default to strnatcmp.

    <?php
    
    $numbers = ['10 Apple', '2 Grapes', '3 Apples', '3.2 Apples', '3.1 Apples', '3.3 Apples', '3.10 Apples', '3.11 Apples', 'Lots of Apples'];
    
    usort($numbers, function ($a, $b) {
        if (preg_match("~^\d*\.\d+\b~", $a, $m)) {
            $aa = (float)$m[0];
    
            if (preg_match("~^\d*\.\d+\b~", $b, $m)) {
                $bb = (float)$m[0];
                return $aa <=> $bb;
            }
        }
    
        return strnatcmp($a, $b);
    });
    print_r($numbers);