Sort a 2d array by a column and obey a dynamic direction variable

I have an array and i want to sort it by value of key [min] (0.2, 0.86 ...) in a desc order. Here is an array:

Array
(
    [0] => Array
        (
            [p1_first_res_avalue] => 0.72413793103448
            [p1_rating_lang_avalue] => 0.2
            [p1_ps_res_avalue] => 0.79310344827586      
            [pid] => 0
            [p1_discipline_e_avalue] => 0.77777777777778
            [p1_rating_lang] => 46
            [p1_first_res] => 59
            [p1_ps_res] => 57
            [p1_discipline_e] => 86
            [min] => 0.2
        )

    [1] => Array
        (
            [p1_discipline_e] => 81
            [p1_first_res] => 55
            [p1_rating_lang] => 38
            [p1_ps_res] => 48
            [p1_discipline_e_avalue] => 1
            [pid] => 1
            [p1_first_res_avalue] => 0.86206896551724
            [p1_rating_lang_avalue] => 1
            [p1_ps_res_avalue] => 1
            [min] => 0.86
        )

   [2] => Array
        (
            [p1_discipline_e] => 81
            [p1_first_res] => 55
            [p1_rating_lang] => 38
            [p1_ps_res] => 48
            [p1_discipline_e_avalue] => 1
            [pid] => 1
            [p1_first_res_avalue] => 0.86206896551724
            [p1_rating_lang_avalue] => 1
            [p1_ps_res_avalue] => 1
            [min] => 0.3
        )
...
)

I've tried to use uasort function, but I can't get access to [min] value of array to compare it. That's what i try ($res is an array, need to sort):

$sortd = 'down';
$f = function($a, $b) use ($sortd) {
        if (($sortd) == 'down') {
            if ($a['min'] == $b['min']) return 0;
            return ($a['min'] > $b['min']) ? -1 : 1;
        }
        else {

        }
    };

foreach ($res as $k => $v) {
    uasort($res[$k], $f);
}

Please, any ideas how to solve the problem?

Your problem seems to be that you're trying to apply the sorting function to each element of the array individually, instead of the array as a whole.

Instead of

foreach ($res as $k => $v) {
    uasort($res[$k], $f);
}

Try just

uasort($res, $f);