如何对来自Facebook生日API的结果进行排序

感谢您的评论-这帮助我朝着正确的方向前进，这就是答案：

        $frnd = $facebook ->api('/me/friends?fields=id,name,birthday&access_token='.$access_token);
        $arr = $frnd["data"];
        function so ($a, $b) {
            $a_dt = explode("/",$a['birthday']); // dt[0] is month, dt[1] is day
            $b_dt = explode("/",$b['birthday']); // dt[0] is month, dt[1] is day
            $a_dt_time = mktime(0,0,0,$a_dt[0],$a_dt[1], date("y"));
            $b_dt_time = mktime(0,0,0,$b_dt[0],$b_dt[1], date("y"));
            return ($a_dt_time < $b_dt_time) ? -1 : 1;
        }
        uasort($arr, 'so');
        $frnd["data"] = $arr;
        // debug: print_r($arr);