无法在codeigniter中使用preg_replace重命名文件

Question

如果文件包含字符，我想上传文件并删除字符，但是如果我尝试使用preg_replace删除文件，则该文件将不起作用并保留原始名称

有人可以帮我吗？

function add_attachment()
        {

            $config['upload_path'] = './myfile/';
            $config['allowed_types'] = 'pdf|xlsx|xls|csv|doc|docx';
            $config['no_space'] = TRUE;
            $config['file_name'] = preg_replace('/[^a-zA-Z0-9.]/','',basename($_FILES['files']['name']));

            $this->load->library('upload', $config);
            $this->upload->initialize($config);

            if ( ! $this->upload->do_upload('file_upload'))
            {
                print_r($this->upload->display_errors());
            }
            else
            {
                $filename = $this->upload->data();
                $file = $filename['file_name'];

                $id = $this->uri->segment(3);
                $idc = $this->uri->segment(4);

                $data = array(
                    'id_request' => $id,
                    'file_name' => $file,
                    'status_confidential' =>$this->input->post('status_confidential')
                );

                $this->request_model->add_request_file($data);

                redirect('request/view_request/'.$id.'/'.$idc);
                $this->db->close();
            }
        }