Question

Consider the following associative array

$arr = Array
(        
    [banana] => 2
    [cherry] => 1
    [orange] => 3
    [grapefruit] => 1
    [apple] => 1
)

I want to sort it in a way that would be similar to the PLSQL term: A DESC, B ASC
(where A is the value and B is the key) meaning:

$arr = Array
(
    [orange] => 3
    [banana] => 2
    [apple] => 1
    [cherry] => 1
    [grapefruit] => 1        
)

so that orange and banana are first because of the VALUE, but then I have apple, cherry and grapefruit in alphabetical order because they have the same VALUE.

What I tried:

1. to run ksort() and then asort()/rsort() hoping that the second sort will bump up orange and banana to the beginning of the array without messing up the alphabetical sort of the other 3 items. I was wrong. it does messes everything up. So I checked out:
2. sort functions and array_multisort(). But apparently it sorts several arrays at once, or a multi-dimensional array.

3. I also tried to define the following compare function:

function cmp($a, $b)
{
    foreach ($a as $key1 => $val1) {
        foreach ($b as $key2 => $val2) {
            if($val1 == $val2){
                return strcmp($key1,$key2);
            }
            else if ($val1 > $val2){
                return 1;
            }
            else{ // $val1 < $val2
                return -1;
            }
        }
    }    
} 

and call it with usort() but it also didn’t work.

So my question is: is there a PHP method that implements the requested behavior?

For Eugen:
I tried it and it doesn’t work
before sorting:

Array
(
    [lamb] => 3
    [rule] => 1
    [children] => 1
    [teacher] => 2
    [eager] => 1
)

and after sorting:

Array
(
    [children] => 1
    [eager] => 1
    [rule] => 1
    [teacher] => 2
    [lamb] => 3
)

Answer 1

You can use array_multisort

<?php
    $arr = Array
    (        
        'banana' => 2,
        'cherry' => 1,
        'orange' => 3,
        'grapefruit' => 1,
        'apple' => 1
    );

    $values = array_values($arr);
    $keys = array_keys($arr);

    //first sort by values desc, then sort by keys asc
    array_multisort($values, SORT_DESC, $keys, SORT_ASC, $arr);

    print_r($arr);
    // output:
    /*
    Array
    (
        [orange] => 3
        [banana] => 2
        [apple] => 1
        [cherry] => 1
        [grapefruit] => 1
    )
    */

?>

It works like this:

• for each column used to sort (values and keys for you), create new 1d array with its contents
• pass those 1d arrays to array_multisort function in your sorting order (so $values first, then $keys), add sort order for each array
• the last argument has to be the array which you want to sort

(Perhaps you will find this explanation easier to understand)