Sort an array of arrays so that larger arrays ar first without preserving first level indexes

Question

$arr1 = [1, 2, 3, 8];
$arr2 = [1, 2, 4, 9, 10];
$arr3 = [1, 2, 5, 11, 12];
$arrs = [$arr1, $arr2, $arr3];
arsort($arrs);

I have sorted the $arrs to change it to $arr3, $arr2, $arr1, My problem is that it kept its Array Key as it is, I want to rewrite these keys by its new order, so instead of

[2]$arr3 [1]$arr2 [0]$arr1

it becomes

[0]$arr3 [1]$arr2 [2]$arr1

I thought about explode()ing then implode()ing the array again But it didn't work because it is a MDArray like the following $arrs = implode(explode($arrs)); after arsort().

What is the best and shortest way to re[write][make] the array keys?

Why not simply use rsort() then? It's the a part of arsort() that's maintaining the original keys — Mark Baker
– Mark Baker, Commented Nov 8, 2017 at 12:14
So if you needed alternative sorting than simply reversal, you shouldn't be using either rsort() or arsort() — Mark Baker
– Mark Baker, Commented Nov 8, 2017 at 12:17
usort($arrs, function($a, $b) { return count($b) - count($a); }); sorts by count of values and resets the keys..... uasort($arrs, function($a, $b) { return count($b) - count($a); }); sorts by count of values and retains the original keys.... where's the problem? — Mark Baker
– Mark Baker, Commented Nov 8, 2017 at 12:22
Use the correct sort function, and you don't have the problem at all, don't need to do any kludgy workround to reset keys after the sort — Mark Baker
– Mark Baker, Commented Nov 8, 2017 at 12:26
Use the correct sort in the first place.... one function, not two functions, that's only the overhead of one function call, not two function calls; the code is readable, short, concise; it does exactly what is necessary, no more, no less... KISS — Mark Baker
– Mark Baker, Commented Nov 8, 2017 at 12:28

mega6382 · Accepted Answer · 2017-11-08 12:15:01Z

3

Just simply use array_values;

$arr1 = [1, 2, 3, 8];
$arr2 = [1, 2, 4, 9, 10];
$arr3 = [1, 2, 5, 11, 12];
$arrs = [$arr1, $arr2, $arr3];
arsort($arrs);

$arrs  = array_values($arrs);

This will reset the keys based on the order.

answered Nov 8, 2017 at 12:15

mega6382

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mega6382 · Accepted Answer · 2017-11-08 12:17:28Z

1

Answer recommended by PHP Collective

You only need rsort if you don't need to keep key

$arr1 = [1, 2, 3, 8];
$arr2 = [1, 2, 4, 9, 10];
$arr3 = [1, 2, 5, 11, 12];
$arrs = [$arr1, $arr2, $arr3];
rsort($arrs);
print_r($arrs);

DEMO

edited Nov 8, 2017 at 12:17

mega6382

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answered Nov 8, 2017 at 12:14

B. Desai

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3 Comments

AXAI Over a year ago

That would work If i just want to reverse the values, But i'm trying to order the array by the highest count array, then change the keys values to be as same as the new order.

mickmackusa Jan 14 at 21:55

rsort() DOES sort subarrays by count first then by values if necessary.

mickmackusa Jan 14 at 22:02

Sort a multidimensional array descending by subarray count and preserve first level keys

Mohyaddin Alaoddin · Accepted Answer · 2017-11-08 12:15:22Z

0

I think you need to use rsort() instead of arsort() because, the latter will preserve the indices when sorting, while the first will reorder the values regardless of the keys.

answered Nov 8, 2017 at 12:15

Mohyaddin Alaoddin

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1 Comment

AXAI Over a year ago

Yes, But the problem is that i want the keys to be changed and not oversee it.

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