How to sort an associative array by a particular key?

cmayo

I must be making this too hard... if I have the following array:

print_r($field);

Array
(
    [19] => Array
        (
            [type] => choice
            [name] => slow
            [label] => Slow
            [value] => -5
            [sort] => 3
            [presentation] => 
        )

[20] => Array
    (
        [type] => choice
        [name] => fast
        [label] => Fast
        [value] => 5
        [sort] => 1
        [presentation] => 
    )
)

how can I sort it by the values in 'sort' so that the order of the array becomes

print_r($field);

Array
(
 [20] => Array
        (
            [type] => choice
            [name] => fast
            [label] => Fast
            [value] => 5
            [sort] => 1
            [presentation] => 
        )

 [19] => Array
        (
            [type] => choice
            [name] => slow
            [label] => Slow
            [value] => -5
            [sort] => 3
            [presentation] => 
        )
   )

Thanks for any tips!

aaron_karp

Have you looked at ksort?

cmayo

Yeah, and usort and array_multisort -- not having much luck making sense of any of it, though.

bubblenut

ksort won't help in this particular situation. You can use either usort (you can use usort for pretty much anything) but I would suggest using array_multisort, here's how it's done.

//First build a simple 2d array of the
//values you wish to sort by
foreach($field as $val) {
  $sortby[]=$val['sort'];
}

//then run them through array_multisort
array_multisort($sortby, SORT_ASC, SORT_NUMERIC, $field);

HTH
Bubble

cmayo

Bubble, thanks for the reply, but I'm having the same difficulty with your suggestion as with the other solutions I've coded, the initial keys are lost after sorting and I really need to keep those, because they're sql record id's.

In other words, instead of:

[20] => Array 
        ( 
            ...
            [sort] => 1 
            ...
        ) 

 [19] => Array 
        ( 
            ...
            [sort] => 3 
            ...
        ) 
   )

I get:

[0] => Array 
        ( 
            ...
            [sort] => 1 
            ...
        ) 

 [1] => Array 
        ( 
            ...
            [sort] => 3 
            ...
        ) 
   )

I think that instead of using the record id's as the initial index, I'll code it to use a throwaway index and put the record key into the subarray, so instead of:

while(...){
     ...
     $field_array[$id]['sort'] = "$field_sort";
     ...
     $ndx++;
}

I'll use

$ndx=0;

while(...) {
    ...
    $field_array[$ndx]['id']=$id;
    $field_array[$ndx]['sort']=$sort;
    ...
}

then it won't matter that the index is reordered

Thanks again for the tip