Laravel – create array of objects and arrays in PHP

I am trying to create an array of objects in laravel php. I have achieved this so far.

but it end up creating a singlee object instead of an array…

I get this output

  $usersData = User::where('user_id', 2)->where("stud_class", $exam_details->exam_class_id)->where("XXXX", $exam_details->exam_branch_id)->get(['name', 'id']);
        foreach ($usersData as $user) {
            $studentsArray = array(
                "student" => $user->name,
                "subjects" => []
            );
            foreach ($exam_data as  $subject) {
                $att_exams =  MODEL::where('XXXXX', $subject->subject_id)
                    ->where('XXXX', $user->id)
                    ->first();
                if ($att_exams) {
                    $marks =  MODEL::where('XXXX', $att_exams->attended_exams_id)->get();
                    $right = 0;
                    $wrong = 0;
                    $total_marks = $marks->sum('XXXX');
                    foreach ($marks as $mark) {
                        if ($mark->XXX== 0) {
                            $wrong++;
                        } else {
                            $right++;
                        }
                    }
                    $total_negative_marks = $wrong * $subject->negative_marks;
                    $subjectsArray[] = array(
                        "subject" => $subject->subject_name,
                        "marks_" => $total_marks - $total_negative_marks,
                    );
                } else {
                    $subjectsArray[] = array(
                        "subject" => $subject->subject_name,
                        "marks_" => 0,
                    );
                }
            }
            $studentsArray["subjects"] = array($subjectsArray);
        }
        return $studentsArray;