這段代碼可以:
1，同時上傳5張圖片
2，同時生成兩種尺寸的縮略圖
3，保存到mysql

controllers：upload.php

<?php
class Upload extends Controller {
  function go() {
    if(isset($_POST['go'])) {
      //初始化
      $config['upload_path'] = 'album/source';
      $config['allowed_types'] = 'gif|jpg|png|bmp|jpeg';
      $config['encrypt_name'] = TRUE;
      $config['remove_spaces'] = TRUE;
      $config['max_size']  = '0';
      $config['max_width']  = '0';
      $config['max_height']  = '0';
     
      $this->load->library('upload', $config);
 
      //170*170圖片
      $configThumb = array();
      $configThumb['image_library'] = 'gd2';
      $configThumb['source_image'] = '';
      $configThumb['create_thumb'] = TRUE;
      $configThumb['maintain_ratio'] = TRUE; //保持圖片比例
      $configThumb['new_image'] = 'album/thumb';
      $configThumb['width'] = 170;
      $configThumb['height'] = 170;
      //600*600圖片
      $configLarge = array();
      $configLarge['image_library'] = 'gd2';
      $configLarge['source_image'] = '';
      $configLarge['create_thumb'] = TRUE;
      $configLarge['maintain_ratio'] = TRUE; //保持圖片比例
      $configLarge['new_image'] = 'album/large';
      $configLarge['width'] = 600;
      $configLarge['height'] = 600;
     
      $this->load->library('image_lib');
 
     
      for($i = 1; $i < 6; $i++) {
       
        $upload = $this->upload->do_upload('image'.$i);
       
        if($upload === FALSE) continue;
       
        $data = $this->upload->data();//返回上傳文件的所有相關信息的數組
       
        $uid = $this->session->userdata('uid');
       
 
 
        $uploadedFiles[$i] = $data;
       
        if($data['is_image'] == 1) {
          //初始化170*170 
          $configThumb['source_image'] = $data['full_path']; //文件路徑帶文件名
          $this->image_lib->initialize($configThumb);
          $this->image_lib->resize();
          //初始化600*600
          $configLarge['source_image'] = $data['full_path']; //文件路徑帶文件名
          $this->image_lib->initialize($configLarge);
          $this->image_lib->resize();
        }
       
        //插入圖片信息到album表,插入的文件名為source目錄文件名
        $picture = array(
            'filename' => $data['file_name'],
            'albumID' => $this->uri->segment(4,0),
            'uid' => $this->session->userdata('uid'),
            'dateline' => time(),
            'describe' => '',
            'click' => 0
        );
       
        $this->load->model('album_model');
        $this->album_model->AddPic($picture);
        $picture = array();
       
       
      }
    }
    
    
    /* 轉出 */
    $albumID = $this->uri->segment(4);
    $backurl = site_url() . 'photo/editpic/album/' .$albumID;
    $this->session->set_flashdata('msg','圖片上傳成功.');
    redirect($backurl,'refresh');
  }
}

views:new_pic.view

<form method="post" action="<?php echo site_url() ?>photo/upload/go/<?php echo $albumID ?>" enctype="multipart/form-data">
  <input type="file" name="image1" class="files"/><br />
  <input type="file" name="image2" class="files"/><br />
  <input type="file" name="image3" class="files"/><br />
  <input type="file" name="image4" class="files"/><br />
  <input type="file" name="image5" class="files"/><br />
  <br />
  <p><input type="submit" name="go" value="上傳照片" class="button" /></p>
</form>

1，要一次上傳幾個文件，修改表單和控制器中循環部分的參數就好。
2，album\\source 是上傳后原圖目錄  large和thumb分別是兩次執行$this->image_lib->resize();后存放縮略圖的目錄
3，縮略圖文件名如需和album\\source目錄一致，請添加參數 $config['thumb_marker'] = '';
3，$picture這部分數組是保存到數據庫的東西，可以不用管了。