public function test()
 {
     $groups = DepartmentSubject::Where('department_id', 1)->groupBy('group')->lists('group');
     foreach ($groups as $group) {
         ${$group} = $department_subjects = DepartmentSubject::Where('department_id', 1)->where('group', $group)->get();
     }
     $data = [];
     foreach ($groups as $group) {
         $data[$group] = ${$group};
     }
     $data['groups'] = $groups;
     return view('test', $data);
 }
 public function single_department($department_id)
 {
     $groups = DepartmentSubject::Where('department_id', $department_id)->groupBy('group')->lists('group');
     $department_name = DepartmentSubject::find($department_id)->department->department_name;
     foreach ($groups as $group) {
         ${$group} = $department_subjects = DepartmentSubject::Where('department_id', $department_id)->where('group', $group)->get();
     }
     $data = [];
     foreach ($groups as $group) {
         $data[$group] = ${$group};
     }
     $data['groups'] = $groups;
     $data['department_name'] = $department_name;
     return view('admin.department_subject.department_subject_single', $data);
 }