Trying to Insert data into DB with IF statement and foreach loop

Question

This insertion code is for assigning "Subjects to the Class". My controller is ok, web.php is ok, and I have cross-checked my model and database table. But I don't know why this code is not working for insertion. When I remove the IF statement and foreach loop, then it works. Otherwise, it does not show a success message and goes to the next page.

public function insert(Request $request)
{
    if (!empty($request->subject_id)) {
        foreach ($request->subject_id as $subject_id) {
            $save = new ClassSubjectModel;
            $save->class_id = $request->class_id;
            $save->subject_id = $subject_id;
            $save->status = $request->status;
            $save->created_by = Auth::user()->id;
            $save->save();
        }

        return view ('admin/assign_subject/list')->with('success', "Subject Successfully Assigned to Class");
    } else {
        return redirect()->back()->with('error', 'No subject selected. Please try again.');
    }
}