/**
 * 上传图片，默认大小限制为3M
 * @param String $fileInputName
 * @param number $size
 */
public function processUpload($fileInputName,$size=3145728)
{
  $result = array('status'=>0, 'errcode'=>null, 'group'=>'', 'path'=>'', 'site'=>'', 'size'=>0);
  $file = $_FILES[$fileInputName];
  //用filesize函数获取文件大小,filesize这个内置函数不能直接放$fileInputName或者$file['name']，要用$file['tmp_name']，或者直接用$file['size']
  $bytes = $file['size'];
  if($bytes==0 || $bytes > $size){
    $result['status'] = -1;
    $result['size'] = $bytes;
    return $result;
  }
  $fileMIME = $file['type'];
  $originFilename = $file['name'];
  $tmpFileDir = C('FILE_UPLOAD_SWAP_DIR');
  $fileName = CommonUtil::generateUUid();
  switch ($fileMIME)
  {
    case 'image/jpeg': //jpeg jpg jpe
      $tmpFile = $tmpFileDir.$fileName.'.jpg';
      break;
    case 'application/x-jpg':
      $tmpFile = $tmpFileDir.$fileName.'.jpg';
      break;
    default:
      $result['status'] = 1;
      $result['group'] = $tmpFileDir.$fileName;
      $result['site'] = $fileMIME;
      return $result;
  }
  //......
}

/**
 * 上传多张图片公共方法
 * fileName 为input的name属性
 */
public function doUploadJpgMultiple()
{
  $filename = I('get.fileName','');
  $uploader = new UploadJpgUtil();
  $result = $uploader->processUpload($filename);
  echo json_encode($result);
}

//一个页面上传多张图片
function ajaxUploadMultiple(j) {
  $.ajaxFileUpload({
    url : base_url+"/UploadImgUtil/doUploadJpgMultiple"+ j,
    secureuri : false,
    fileElementId : "fileToUpload"+ j,// file控件id
    type: "POST",
    dataType: 'json',
    success : function(data, status) {
      if (typeof (data.status) != 'undefined') {
        if (data.status == -1) {
          alert('上传图片不能超过规定大小');
        }else if (data.status == 1) {
          alert('上传图片不是JPG格式');
        }else if (data.status != 0) {
          alert('status='+data.status + ' errcode=' + data.errcode);
        }
        else {
          var fileUrl = 'http://' + data.site + '/' + data.group
            + '/' + data.path;
          $('#flatImgthumb'+ j).attr('src', fileUrl);
          $('#hidFlatImgthumb'+ j).val(data.group + '/' + data.path);
        }
      }
    },
    error : function(data, status, e) {
      alert(e);
    }
  });
  return false;
}