Page search result does not load results! I cannot find the error!

Question

I type the name in the search field and click search the screen is cropped as in the image below. When I refresh the page the result appears and quickly disappears. I made a gif below showing the problem:

Code used in the controller (Codeigniter).

    // Details of searched student
function student_details($param1 = ""){
  if ($this->session->userdata('admin_login') != 1)
      redirect(site_url('login'), 'refresh');

  $student_identifier = html_escape($this->input->post('student_identifier'));
  $query_by_code = $this->db->get_where('student', array('student_code' => $student_identifier));

  if ($query_by_code->num_rows() == 0) {
    $this->db->like('name', $student_identifier);
    $query_by_name = $this->db->get('student');
    if ($query_by_name->num_rows() == 0) {
      $this->session->set_flashdata('error_message' , get_phrase('no_student_found'));
      redirect(site_url('admin/dashboard'), 'refresh');
    }
    else{
      $page_data['student_information'] = $query_by_name->result_array();
    }
  }
  else{
    $page_data['student_information'] = $query_by_code->result_array();
  }
  $page_data['page_name']   = 'search_result';
    $page_data['page_title']    = get_phrase('search_result');
    $this->load->view('backend/index', $page_data);
}