How to upload file ?

[eluser]mahe11[/eluser]
Hi All,
By using codeIgniter user guide it work. But when i try it in my controller then it cant work. so tell me which things i forget.

Code:

public  function savenew(){                
                
                $config['upload_path'] = base_url().'uploads/';
        $config['allowed_types'] = 'gif|jpg|png';
        $config['max_size']    = '2048';
        $config['max_width']  = '1024';
        $config['max_height']  = '768';
        
        $this->load->library('upload', $config);
    
        if ( ! $this->upload->do_upload())
        {
                   echo "error... ";
                    $data['error']= array('error' => $this->upload->display_errors());
                    }
                    else
                        {
                        echo 'file upload....';
                        $data = array('upload_data' => $this->upload->data());
                        
                        }
                
            }

Plz help me......