PHP排序疑点

function switchWeek($num){

    switch ($num) {

        case 1:

            return '星期一';

            break;

        case 2:

            return '星期二';

            break;

        case 3:

            return '星期三';

            break;

        case 4:

            return '星期四';

            break;

        case 5:

            return '星期五';

            break;

        case 6:

            return '星期六';

            break;

        case 7:

            return '星期日';

            break;

         default:

            return '';

            break;

    }

}

$con = mysql_connect("localhost","root","") or die('连接失败:'.mysql_error());

mysql_select_db("testt");

mysql_query('set names utf8');

$sql = 'select * from news ';

$result = mysql_query($sql);

$array = array();

while($row = mysql_fetch_array($result,MYSQL_ASSOC)){

    $key = date('Y年m月d日',$row['sTime']).' '.switchWeek(date('N',$row['sTime']));

    $array[$key][]=$row;

}

mysql_free_result($result);

//var_dump($array);

?>