$config['upload_path']    = FCPATH.'public/uploads/';
    $config['allowed_types']  = 'gif|jpg|png';
    $config['overwrite']      = true;
    $this->load->library('upload', $config);
    $this->upload->initialize($config);
    if ( ! $this->upload->do_upload('file'))
    {
        print_r($this->upload->display_errors());
    }

Message: is_uploaded_file() expects parameter 1 to be string, array given