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Say I have a multi-dimensional array set up as follows: 

$matrix[1][1]=4.54;        $matrix[2][1]="apples";  $matrix[3][1]="coles";
$matrix[1][2]=7.2140230;   $matrix[2][2]="apples";  $matrix[3][2]="safeway";
$matrix[1][3]=15.56;       $matrix[2][3]="oranges"; $matrix[3][3]="coles";
$matrix[1][4]=2.34;        $matrix[2][4]="bananas"; $matrix[3][4]="safeway";
$matrix[1][5]=27.98;       $matrix[2][5]="grapes";  $matrix[3][5]="coles";
$matrix[1][6]=17.68493403; $matrix[2][6]="oranges"; $matrix[3][6]="safeway";

And I wish to re-arrange by the pricing information which I've stored under the first 1st column, so that the new order of $matrix would be:

$matrix[1][1]=2.34;        $matrix[2][1]="bananas"; $matrix[3][1]="safeway";
$matrix[1][2]=4.54;        $matrix[2][2]="apples";  $matrix[3][2]="coles"; 
$matrix[1][3]=7.2140230;   $matrix[2][3]="apples";  $matrix[3][3]="safeway";
$matrix[1][4]=15.56;       $matrix[2][4]="oranges"; $matrix[3][4]="coles";
$matrix[1][5]=17.68493403; $matrix[2][5]="oranges"; $matrix[3][5]="safeway";
$matrix[1][6]=27.98;       $matrix[2][6]="grapes";  $matrix[3][6]="coles";

What would be the best way to achieve this? I've read other questions about sorting multi-dimensional arrays but have had trouble implementing because those examples seemed to have associative arrays with keys and elements, whereas I am just using the different numbers to store each piece of data. I would prefer not to change the way I am storing data in the array as the actual script is quite long and complex and so this would involve a lot of re-work.

I am completely new to PHP so my apologies if I am missing something obvious here. Thanks for your help.

EDIT: Thanks everyone for your advice, scessors code is exactly what I needed. Halfer - to your 1st question - Yes, 2nd post - good point, I will implement this. Thanks again everyone!

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Is the first index 1=price, 2=product, 3=store, for both input and output arrays? Thanks @kapep for a much better formatting, that makes it clearer! – halfer Feb 3 at 14:49
Can you change the data format? This would be much easier if the first number was the "product ID" and the last number was the price/name/supplier index. – slugonamission Feb 3 at 14:51
I appreciate you don't want to change your approach, but just for the record it might be better if you were to swap your [X][Y] ordering to [Y][X]. That way an array in $matrix[1] would contain the price, product and store, and thus is an 'object' that can be more easily sorted. – halfer Feb 3 at 14:52
@user2037290 First question here, please read what to do when you get answers. – DoSparKot Feb 3 at 15:01

3 Answers

up vote 2 down vote accepted

If it's no problem that the sorted array begins with zero, you can use array_multisort:

array_multisort(
    $matrix[1], SORT_ASC, SORT_NUMERIC,
    $matrix[2], SORT_ASC, SORT_STRING,
    $matrix[3], SORT_ASC, SORT_STRING
);

Also see my example.

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What if you want to leave the original array intact? Just make a copy? – Strawberry Feb 3 at 15:16
Yes, also see this example. – scessor Feb 3 at 15:26
up vote 0 down vote

I believe that phps array_multisort will do it for you:

Heres an example from docs:

<?php
$ar1 = array(10, 100, 100, 0);
$ar2 = array(1, 3, 2, 4);
array_multisort($ar1, $ar2);

var_dump($ar1);
var_dump($ar2);
?>

In this example, after sorting, the first array will contain 0, 10, 100, 100. The second array will contain 4, 1, 2, 3. The entries in the second array corresponding to the identical entries in the first array (100 and 100) were sorted as well.

From: http://php.net/manual/en/function.array-multisort.php

share|improve this answer
Sorry that my answer would mean splitting your arrays :-( – DEzra Feb 3 at 14:45
Thanks for your help DEzra – user2037290 Feb 3 at 15:38
No problem, glad you got an answer. – DEzra Feb 6 at 21:04
up vote 0 down vote

Using my_uksort provided by Adam Backstrom

<?php
function my_uksort($a, $b) {
    global $matrix;
    asort($matrix[1]); 
    return $matrix[1][$a] < $matrix[1][$b] ? -1 : 1;
}

uksort($matrix[2], 'my_uksort');
uksort($matrix[3], 'my_uksort');

print_r($matrix);
?>

DEMO

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