get upload error codeigniter

1if($this->input->post())
2{
3   $file_element_name = 'image';  //this is the name of your input file. for example "image"
4   if ($_FILES['image']['name']!= "")
5   {
6      $config['upload_path'] = './uploads/';
7      $config['allowed_types'] = 'gif|jpg|png|exe|xls|doc|docx|xlsx|rar|zip';
8      $config['max_size']      = '8192'; 
9      $config['remove_spaces']=TRUE;  //it will remove all spaces
10      $config['encrypt_name']=TRUE;   //it wil encrypte the original file name
11      $this->load->library('upload', $config);
12
13      if (!$this->upload->do_upload($file_element_name))
14      {
15         $error = array('error' => $this->upload->display_errors());
16         $this->session->set_flashdata('error',$error['error']);
17         redirect('controller_name/function_name','refresh');
18      }
19      else
20      {
21         $data = $this->upload->data();
22         return $data['file_name'];          
23      }
24      $this->session->set_flashdata('msg','success message');
25      redirect('controller_name/function_name','refresh');
26   }
27   else
28   {
29        //if no file uploaded the do stuff here
30   } 
31}