PHP求某二维数组，某一列元素的最大最小值

$box = array(  0 =>array(     'boxnum' => 1,     'record' => 66    ),  1 =>array(     'boxnum' => 2,     'record' => 66    ),  2 =>array(     'boxnum' => 3,     'record' => 66    ))//求boxnum这一列的最大值$max = 0;foreach ($box as $key => $val) {  $max = max($max , $val['boxnum']);}//求boxnum这一列的最小值$min = 0;foreach ($box as $key => $val) {  $min = min($min , $val['boxnum']);}