PHP - 从数组中获取min（）/ max（）值

I have some array like this

$arr_dt = array();

foreach ($dt as $r){
    $arr_dt[$r->criteria][$r->alternative] = $r->value;
}

How can i get min / max value based on criteria or alternative?

the criteria may have same value, like below

$arr_dt[criteria1][alternative1] = 25;
$arr_dt[criteria1][alternative2] = 64;
$arr_dt[criteria1][alternative3] = 46;
$arr_dt[criteria2][alternative1] = 80;
$arr_dt[criteria2][alternative2] = 100;
$arr_dt[criteria2][alternative3] = 25;

how can i get max value of criteria 1 and criteria 2.

Thank You very much.

Get the max value:

 $value = max($array);

Get the corresponding key:

 $key = array_search($value, $array);

Try this.