Php 如何在Select语句laravel 5.1中编写子查询？

如何在laravel 5.1中编写此查询

SELECT 
     (SELECT firstname FROM registration_details a INNER JOIN users b 
        ON a.id = b.registerid
        WHERE c.patientid = b.id ) AS patient,
     (SELECT firstname FROM registration_details a INNER JOIN users b 
        ON a.id = b.registerid 
        WHERE c.doctorid = b.id ) AS doctor, 
    c.`appoinmentdate`
FROM `appoinments` c

我尝试这样做，但得到未定义的属性：stdClass:：$id错误

 DB::table('appoinments')
   ->select(DB::raw(
       "(SELECT firstname FROM registration_details INNER JOIN users ON      registration_details.id = users.registerid WHERE appoinments.patientid =    users.id) AS patient",
       "(SELECT firstname FROM registration_details INNER JOIN users ON registration_details.id = users.registerid WHERE appoinments.doctorid = users.id) As doctor",
       "appoinments.appoinmentdate",
       "appoinments.id",
       "(SELECT timings FROM appoinment_time WHERE appoinment_time.id = appoinments.appoinment_time) AS apptime ",
       "(SELECT branchname FROM branches WHERE branches.id = appoinments.branchcode) AS branch"))
  ->get();

---

终于得到了答案。感谢所有为我努力的人

$appoinment = DB::table('appoinments')->select(DB::raw("(SELECT firstname FROM registration_details INNER JOIN users ON registration_details.id = users.registerid WHERE appoinments.patientid = users.id) AS patientid"));
$appoinment = $appoinment->addSelect(DB::raw("(SELECT firstname FROM registration_details INNER JOIN users ON registration_details.id = users.registerid WHERE appoinments.doctorid = users.id) As doctorid"));
$appoinment = $appoinment->addSelect(DB::raw("appoinments.appoinmentdate"));
$appoinmentlist = $appoinment3->addSelect(DB::raw("appoinments.id"))->get();