public function updateAttendance(Request $request)
 {
     $course_id = $request->get('course_id');
     $session_name = $request->get('session');
     $day = $request->get('date');
     $trainee_ids = Info::whereCourse_id($course_id)->lists('trainee_id');
     foreach ($trainee_ids as $trainee_id) {
         $attendance = Attendance::wheretrainee_id($trainee_id)->whereCourse_id($course_id)->whereSession_name($session_name)->where('day', '=', Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $day . ' 00:00:00'))->firstorFail();
         $attendance->trainee_attendance = $request->get('ta__' . $trainee_id);
         $attendance->update();
     }
     $presents = Attendance::whereCourse_id($course_id)->whereSession_name($session_name)->where('day', '=', Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $day . ' 00:00:00'))->where("trainee_attendance", "P")->select('trainee_id')->get();
     $present_att = array();
     $i = 0;
     foreach ($presents as $present) {
         $present = Info::whereTrainee_id($present->trainee_id)->select('name')->firstorFail();
         $present_att[$i++] = $present->name;
     }
     $absents = Attendance::whereCourse_id($course_id)->whereSession_name($session_name)->where('day', '=', Carbon\Carbon::createFromFormat('Y-m-d H:i:s', $day . ' 00:00:00'))->where("trainee_attendance", "A")->select('trainee_id')->get();
     $absent_att = array();
     $j = 0;
     foreach ($absents as $absent) {
         $absent = Info::whereTrainee_id($absent->trainee_id)->select('name')->firstorFail();
         $absent_att[$j++] = $absent->name;
     }
     $course_name = $this->course_name_by_course_id($course_id);
     $session = $request->get('session');
     $date = $request->get('date');
     return view('attendances.attendance_show', compact('present_att', 'absent_att'))->with('date', $date)->with('session', $session)->with('course_name', $course_name)->with('course_id', $course_id);
 }