Sort a 2d array by a dynamically determined column

Question

I have an array in php :

$myarray[$index]['height']
$myarray[$index]['weight']
$myarray[$index]['age']

which is the best function to sort by any of the key 'height', 'weight' or 'age'?

An an example, if I have in input

$myarray[0]['height'] = 175;
$myarray[0]['weight'] = 68;
$myarray[0]['age'] = 44;

$myarray[1]['height'] = 166;
$myarray[1]['weight'] = 82;
$myarray[1]['age'] = 56;

$myarray[2]['height'] = 188;
$myarray[2]['weight'] = 82;
$myarray[2]['age'] = 35;

and I want to sort by age, I obtain

$myarray[0]['height'] = 188;
$myarray[0]['weight'] = 82;
$myarray[0]['age'] = 35;

$myarray[1]['height'] = 175;
$myarray[1]['weight'] = 68;
$myarray[1]['age'] = 44;

$myarray[2]['height'] = 166;
$myarray[2]['weight'] = 82;
$myarray[2]['age'] = 56;

usort() passing the column you want to sort on to the callback — Mark Baker
– Mark Baker, Commented Nov 13, 2016 at 21:22

Jeff Puckett · Accepted Answer · 2016-11-13 21:21:45Z

1

There's a great example on the usort documentation for custom sorting multidimensional arrays.

Here's a fiddle.

<?php
$myarray[0]['height'] = 175;
$myarray[0]['weight'] = 68;
$myarray[0]['age'] = 44;

$myarray[1]['height'] = 166;
$myarray[1]['weight'] = 82;
$myarray[1]['age'] = 56;

$myarray[2]['height'] = 188;
$myarray[2]['weight'] = 82;
$myarray[2]['age'] = 35;

function build_sorter($key) {
    return function ($a, $b) use ($key) {
        return strnatcmp($a[$key], $b[$key]);
    };
}

usort($myarray, build_sorter('age'));

print_r($myarray);

Array
(
    [0] => Array
        (
            [height] => 188
            [weight] => 82
            [age] => 35
        )

    [1] => Array
        (
            [height] => 175
            [weight] => 68
            [age] => 44
        )

    [2] => Array
        (
            [height] => 166
            [weight] => 82
            [age] => 56
        )

)

answered Nov 13, 2016 at 21:21

Jeff Puckett

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2 Comments

Ivo Over a year ago

thanks, but is strnatcmp is the right function for comparing numbers?

Jeff Puckett Over a year ago

It works for me, but of course you can modify/substitute it to suit your needs.

sevavietl · Accepted Answer · 2016-11-13 21:36:31Z

0

So basically what you need is to sort an array by column. The following code will do the trick:

function sortByColumn(&$array, $column, $order = SORT_ASC)
{
    array_multisort(
        array_column($array, $column),
        $order,
        $array
    );
}

This approach is using array_multisort and array_column functions.

Also this way you can specify the order (SORT_ASC or SORT_DESC).

Here is working demo.

answered Nov 13, 2016 at 21:36

sevavietl

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