What is wrong with this code pls

Dear Team,
Please this code can run on view but returns zero or null for total_marks and Average score whenever i run it on controller.
Tell me what i am doing wrong. Thanks 

function testme ($exam_id,$class_id){

$soap_data['exam_id'] = $exam_id;
$soap_data['class_id'] = $class_id;

        $soap_data['year']       = $this->db->get_where('settings' , array('type'=>'running_year'))->row()->description;
        if($soap_data['class_id'] != '' && $soap_data['exam_id'] != ''){


$subjects = $this->db->get_where('subject' , array('class_id' => $class_id , 'year' => $running_year))->result_array();
foreach($subjects as $row){ echo $row['name'];}



$students = $this->db->get_where('enroll' , array('class_id' => $class_id , 'year' => $running_year))->result_array();
    foreach($students as $row){

$total_marks = 0;
            $total_grade_point = 0;
                    foreach($subjects as $row2)
$obtained_mark_query = $this->db->get_where('mark' , array(
'class_id' => $class_id , 
'exam_id' => $exam_id , 
'subject_id' => $row2['subject_id'] , 
'student_id' => $row['student_id'],
'year' => $running_year
));
if ( $obtained_mark_query->num_rows() > 0) {
$obtained_marks = $obtained_mark_query->row()->mark_obtained;
if ($obtained_marks >= 0 && $obtained_marks != '') {
$grade = $this->crud_model->get_grade($obtained_marks);
$total_grade_point += $grade['grade_point'];
}
$total_marks += $obtained_marks;

}

$soap_data['Total_score'] = $total_marks;
$this->db->where('class_id' , $class_id);
$this->db->where('year' , $running_year);
$this->db->from('subject');
$number_of_subjects = $this->db->count_all_results();
$average_score= ($soap_data['Total_score'] / $number_of_subjects);
$avg =  round($average_score,2);
$soap_data['Average_score'] = $avg;
}



        $query = $this->db->get_where('total_mark' , array(
                    'exam_id' => $soap_data['exam_id'],
                        'class_id' => $soap_data['class_id'],
                            'Total_score' => $soap_data['Total_score'],
                                'Average_score' => $soap_data['Average_score'],
                                    'year' => $soap_data['year']
                ));
        if($query->num_rows() < 1) {
           $students = $this->db->get_where('enroll' , array('class_id' => $soap_data['class_id'] , 'year' => $soap_data['year']))->result_array();
            foreach($students as $row) {
               $soap_data['student_id'] = $row['student_id'];
                $this->db->insert('total_mark' , $soap_data);
            }
}
}

}