在PHP中，如何基于键[关闭]排序关联数组排序

I've a nested associative array like the one below and need help sorting the array for each of the keys such as 'first_name' and 'score'.

For example:

Array
(
    [12345] => Array
        (
            [75] => Array
                (
                    [first_name] => Xen
                    [score] => 245
                )
        )

    [9876] => Array
        (
            [75] => Array
                (
                    [first_name] => Shane
                    [score] => 300
                )
        ) 
    [4567] => Array
        (
            [75] => Array
                (
                    [first_name] => Dan
                    [score] => 100
                )
        ) 
)

The result should have the array sorted by the keys in ascending order:

Array
(
    [first_name] => Array
                 (
                   [0] => 4567
                   [1] => 9876
                   [2] => 12345
                 )

    [score] => Array
           (
             [0] => 4567
             [1] => 12345
             [2] => 9876
           )
)

ksort is PHP's function to sort by key. So to sort an array $arr by its keys, do:

ksort($arr);

Note that ksort returns a boolean (success or failure), so you shouldn't do $arr = ksort($arr);. ksort modifies the original array.

To sort a multidimensional associative array (say, an associative array of associative arrays) recursively by keys, try the user-provided function at the bottom of the ksort manual page (I haven't tried this, but it looks like it will work just fine):

function deep_ksort(&$arr) {
    ksort($arr);
    foreach ($arr as &$a) {
        if (is_array($a) && !empty($a)) {
            deep_ksort($a);
        }
    }
}