Reverse sort array with rearranging of index

Question

So currently I'm having a problem where I have an array setup like this

array(8) { 
    [0]=> array(2) { 
        [0]=> float(2.1166666666667) 
        [1]=> string(7) "9434493" 
    } 
    [1]=> array(2) { 
        [0]=> float(2.07) 
        [1]=> string(7) "8591971" 
    } 
    [2]=> array(2) { 
        [0]=> float(2.0566666666667) 
        [1]=> string(8) "17015102" 
    } 
    [3]=> array(2) { 
        [0]=> float(2.0366666666667) 
        [1]=> string(7) "9637191" 
    } 
    [4]=> array(2) { 
        [0]=> float(2.015) 
        [1]=> string(8) "11405473" 
    } 
    [5]=> array(2) { 
        [0]=> float(1.9833333333333) 
        [1]=> string(8) "28233403" 
    } 
    [6]=> array(2) { 
        [0]=> float(2.0366666666667) 
        [1]=> string(8) "14248330" 
    } 
    [7]=> array(2) { 
        [0]=> float(2.0933333333333) 
        [1]=> string(8) "14987165" 
    } 
}

After I use the function arsort() it looks like this:

array(8) { 
    [0]=> array(2) { 
        [0]=> float(2.1166666666667) 
        [1]=> string(7) "9434493" 
    } 
    [7]=> array(2) { 
        [0]=> float(2.0933333333333) 
        [1]=> string(8) "14987165" 
    } 
    [1]=> array(2) { 
        [0]=> float(2.07) 
        [1]=> string(7) "8591971" 
    } 
    [2]=> array(2) { 
        [0]=> float(2.0566666666667) 
        [1]=> string(8) "17015102" 
    } 
    [6]=> array(2) { 
        [0]=> float(2.0366666666667) 
        [1]=> string(8) "14248330" 
    } 
    [3]=> array(2) { 
        [0]=> float(2.0366666666667) 
        [1]=> string(7) "9637191" 
    } 
    [4]=> array(2) { 
        [0]=> float(2.015) 
        [1]=> string(8) "11405473" 
    } 
    [5]=> array(2) { 
        [0]=> float(1.9833333333333) 
        [1]=> string(8) "28233403" 
    } 
}

So all cool that my array is sorted by the value of [0] index. But.....

When I try to loop through like this...

$x = 0;
while ($x < count($sorted_array)) {
    $sorted_array[$x][0];
    $x++;
}

It kept printing out the original array order. I then realized when I used the function arsort() it kept the original order of the indexes so that's why it was printing in the original array order.

Is there a function to fix this so I can loop it with an index? Any help will be much appreciated.

Use rsort function instead of arsort, if you don't want to keep index position with value. — Shailesh Chauhan
– Shailesh Chauhan, Commented Feb 18, 2018 at 5:48

mickmackusa · Accepted Answer · 2018-02-18 04:54:20Z

4

When you use arsort() you preserve the keys.

Because you are iterating using $x, you are effectively ignoring your sort call.

Either use rsort() with your loop.

Or use a foreach() loop after your arsort() call.

Or best, just call array_column() instead of looping.

Here are some demonstrations: (Demo Link)

$array=$copy=[
    [2.1166666666667,9434493],
    [2.07,8591971],
    [2.0566666666667,17015102],
    [2.0366666666667,9637191],
    [2.015,11405473],
    [1.9833333333333,28233403],
    [2.0366666666667,14248330],
    [2.0933333333333,14987165]
];
arsort($array);
var_export(array_column($array,0));  // <-- you lose the keys you preserved
echo "\n---\n";

foreach($array as $index=>$row){     // <-- you keep the keys you preserved
    echo "$index : {$row[0]}\n";
}

echo "\n---\n";
rsort($copy);                        // you don't preserve the keys
for($x=0, $count=sizeof($copy); $x<$count; ++$x){  // you should cache the count instead of calling count() on every iteration
    echo "$x : {$copy[$x][0]}\n";
}

Output:

array (
  0 => 2.1166666666667,
  1 => 2.0933333333333,
  2 => 2.07,
  3 => 2.0566666666667,
  4 => 2.0366666666667,
  5 => 2.0366666666667,
  6 => 2.015,
  7 => 1.9833333333333,
)
---
0 : 2.1166666666667
7 : 2.0933333333333
1 : 2.07
2 : 2.0566666666667
6 : 2.0366666666667
3 : 2.0366666666667
4 : 2.015
5 : 1.9833333333333

---
0 : 2.1166666666667
1 : 2.0933333333333
2 : 2.07
3 : 2.0566666666667
4 : 2.0366666666667
5 : 2.0366666666667
6 : 2.015
7 : 1.9833333333333

edited Feb 18, 2018 at 4:54

answered Feb 18, 2018 at 4:45

mickmackusa♦

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1 Comment

Carlitos Over a year ago

I will use one of these methods. I'll let you know how it goes.

Aniket Sahrawat · Accepted Answer · 2018-02-18 04:32:44Z

3

rsort() is great fit here.

Sort an array in reverse order

This function does not maintain index association

answered Feb 18, 2018 at 4:32

Aniket Sahrawat

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Comments

John Halbert · Accepted Answer · 2018-02-18 04:33:33Z

1

A quick look at PHP documentation suggests rsort() would work.

http://php.net/manual/en/array.sorting.php

answered Feb 18, 2018 at 4:33

John Halbert

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