php 二维数组冒泡排序

function mpSort($arr,$key){
                for($i=0;$i<count($arr);$i++){
                    for($j=$i;$j<count($arr);$j++){
                        if($arr[$i][$key]>$arr[$j][$key]){
                            $temp=$arr[$i];
                            $arr[$i]=$arr[$j];
                            $arr[$j]=$temp;
                        }
                    }
                }
                return $arr;
        }

注：$key为要排序的字段