冒泡排序

$arr = [4,5,3,7,8,9];
print_r(maopao($arr));
function maopao($arr){
    $len = count($arr);
    $n = $len-1;
    for ($i=0;$i<=$len;$i++){
        for ($j=0;$j<$n;$j++){
            if ($arr[$j+1]<$arr[$j]){
                $temp = $arr[$j];
                $arr[$j] =  $arr[$j+1] ;
                $arr[$j+1] = $temp;
            }
        }
    }
    return $arr;
}