该程序可以实现:
1.同时上传5张图片
2.同时生成两种尺寸的缩略图
3.保存到mysql

controllers：upload.php文件：

复制代码 代码如下:<?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图片
      $configThumb = array();
      $configThumb["image_library"] = "gd2";
      $configThumb["source_image"] = "";
      $configThumb["create_thumb"] = TRUE;
      $configThumb["maintain_ratio"] = TRUE; //保持图片比例
      $configThumb["new_image"] = "album/thumb";
      $configThumb["width"] = 170;
      $configThumb["height"] = 170;
      //600*600图片
      $configLarge = array();
      $configLarge["image_library"] = "gd2";
      $configLarge["source_image"] = "";
      $configLarge["create_thumb"] = TRUE;
      $configLarge["maintain_ratio"] = TRUE; //保持图片比例
      $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();//返回上传文件的所有相关信息的数组
        $uid = $this->session->userdata("uid");
        $uploadedFiles[$i] = $data;

        if($data["is_image"] == 1) {
          //初始化170*170 
          $configThumb["source_image"] = $data["full_path"]; //文件路径带文件名
          $this->image_lib->initialize($configThumb);
          $this->image_lib->resize();
          //初始化600*600
          $configLarge["source_image"] = $data["full_path"]; //文件路径带文件名
          $this->image_lib->initialize($configLarge);
          $this->image_lib->resize();
        }

        //插入图片信息到album表,插入的文件名为source目录文件名
        $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();
      }
    }

    /* 转出 */
    $albumID = $this->uri->segment(4);
    $backurl = site_url() . "photo/editpic/album/" .$albumID;
    $this->session->set_flashdata("msg","图片上传成功.");
    redirect($backurl,"refresh");
  }
}

views:new_pic.view文件：

复制代码 代码如下:<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="上传照片" class="button" /></p>
</form>

此外需要注意：

1.要一次上传几个文件，修改表单和控制器中循环部分的参数就好。
2.album\source 是上传后原图目录  large和thumb分别是两次执行$this->image_lib->resize();后存放缩略图的目录
3.缩略图文件名如需和album\source目录一致，请添加参数 $config["thumb_marker"] = "";
4.$picture这部分数组是保存到数据库的东西，可以不用管了。