PHP - 如何按总和值对这个多维数组进行排序？

Question

How can I sort this array by the sum value of each set in the deepest nested array?

$arr = Array(
    Array(
        'I am the first string.',
        Array(
            Array( 'round', 1, 1 ),
            Array( 'rhythm', 1, 1 )
        )
    ),
    Array(
        'I am the second string',
        Array(
            Array( 'cps', 1, 1 ),
            Array( 'Hz', 1, 3 ),
            Array( 'hertz', 1, 1 )
        )
    ),
    Array(
        'I am the third string.',
        Array(
            Array( 'uucps', 1, 1 ),
            Array( 'uuHz', 1, 2 ),
            Array( 'uuhertz', 1, 1 )
        )
    )

);

I need to sort the second dimension of arrays by the sum value of third key of the deepest set(third dimension).

So the end result will look like this:

$arr = Array(
    Array(
        'I am the second string',
        Array(
            Array( 'cps', 1, 1 ),
            Array( 'Hz', 1, 3 ),
            Array( 'hertz', 1, 1 )
        )
    ),
    Array(
        'I am the third string.',
        Array(
            Array( 'uucps', 1, 1 ),
            Array( 'uuHz', 1, 2 ),
            Array( 'uuhertz', 1, 1 )
        )
    ),
    Array(
        'I am the first string.',
        Array(
            Array( 'round', 1, 1 ),
            Array( 'rhythm', 1, 1 )
        )
    )

);

I know that usort might be my best bet but I can't seems to make it work for my use case.

Answer 1

The solution using usort , array_sum and array_column functions:

usort($arr, function($a, $b){
    $prev = array_sum(array_column($a[1], 2)); // summing up values for each third key (2)
    $next = array_sum(array_column($b[1], 2));

    return $next - $prev;    
});

print_r($arr);

The output:

Array
(
    [0] => Array
        (
            [0] => I am the second string
            [1] => Array
                (
                    [0] => Array
                        (
                            [0] => cps
                            [1] => 1
                            [2] => 1
                        )
                    [1] => Array
                        (
                            [0] => Hz
                            [1] => 1
                            [2] => 3
                        )
                    [2] => Array
                        (
                            [0] => hertz
                            [1] => 1
                            [2] => 1
                        )
                )
        )
    [1] => Array
        (
            [0] => I am the third string.
            [1] => Array
                (
                    [0] => Array
                        (
                            [0] => uucps
                            [1] => 1
                            [2] => 1
                        )
                    [1] => Array
                        (
                            [0] => uuHz
                            [1] => 1
                            [2] => 2
                        )
                    [2] => Array
                        (
                            [0] => uuhertz
                            [1] => 1
                            [2] => 1
                        )
                )
        )
    [2] => Array
        (
            [0] => I am the first string.
            [1] => Array
                (
                    [0] => Array
                        (
                            [0] => round
                            [1] => 1
                            [2] => 1
                        )
                    [1] => Array
                        (
                            [0] => rhythm
                            [1] => 1
                            [2] => 1
                        )
                )
        )
)