日期加微秒时间加id后四位生成唯一订单号

function build_order_no($uid){    //uid后四位    $uid_len = strlen($uid);    if ($uid_len != 4){        if ($uid_len>4){            $after_uid = substr($uid,-4);        }else{            $after_uid = '';            for ($i = 1 ; $i < (5 - $uid_len) ;$i++){                $after_uid .= 0;            }            $after_uid .= $uid;        }    }else{        $after_uid = $uid;    }    //获得微秒数    $un_number = substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);    return date('ymdhis').$un_number.$after_uid;}复制代码