上传几个图像CodeIgniter时只创建一次缩略图

This is the code:

for ($i=0; $i<$total_count_of_files; $i++)
                {
                    $_FILES['userfile']['name'] = $_FILES['pics']['name'][$i];
                    $_FILES['userfile']['type'] = $_FILES['pics']['type'][$i];
                    $_FILES['userfile']['tmp_name'] = $_FILES['pics']['tmp_name'][$i];
                    $_FILES['userfile']['error'] = $_FILES['pics']['error'][$i];
                    $_FILES['userfile']['size'] = $_FILES['pics']['size'][$i];

                    $config['upload_path'] = './uploads/gallery/';
                    $config['allowed_types'] = 'jpg|jpeg|gif|png';
                    $config['max_size'] = '0';
                    $config['encrypt_name'] = TRUE;

                    $this->upload->initialize($config);

                    if($this->upload->do_upload())
                    {
                        $pic = $this->upload->data();

                        // Thumbnail
                        $config1['image_library'] = 'gd2';
                        $config1['source_image'] = $pic['full_path'];
                        $config1['create_thumb'] = TRUE;
                        $config1['maintain_ratio'] = FALSE;
                        $config1['width'] = 180;
                        $config1['height'] = 113;

                        $this->load->library('image_lib', $config1);
                        $this->image_lib->resize();
                        // Thumbnail ends

                        $count_imgs += 1;
                        $this->galleries_model->add_image($pic['file_name'], $pic['image_width'], $pic['image_height'], $gallery_id);
                    }
                }

The code works fine, just one problem with the thumbnail creation, it makes only one thumb (the first image which is uploaded) and then not create (but continue to upload the other original images fine). what could be the problem?

Thank you.

i think you must be clear image library class after each image creation.

$this->image_lib->resize();
$this->image_lib->clear();