class Upload {
        //确定属性
        private $_max_size;
        private $_ext_list= array('.jpg','.png','.gif');
        private $_allow_mine_list= array('p_w_picpath/pgn','p_w_picpath/gif','p_w_picpath/jpeg','p_w_picpath/pjpeg','p_w_picpath/x-png');
        private $_upload_path;
        private $_prefix;
        public function __construct()
        {
            $this -> setMaxsize(4*1024*1024);
        }
        //给出对应的set方法
        public function setMaxsize($max_size){
            $this->_max_size=$max_size;
        }

        public function setExtList(array $ext_list = array('.jpg','.png','.gif')){
            $this->_ext_list=$ext_list;
        }

        public function setAllowMimeList(array $allow_mine_list=array('p_w_picpath/pgn','p_w_picpath/gif','p_w_picpath/jpeg','p_w_picpath/pjpeg','p_w_picpath/x-png')){
            $this->_allow_mine_list=$allow_mine_list;
        }

        public function setUploadPath ($upload_path){
            $this->_upload_path=$upload_path;
        }
        public function setPrefix($prefix){
            $this->_prefix=$prefix;
        }

        public function doUpload($tmp_file){
            //判断文件大小，当文件过大时给出提示，放弃上传
            if($tmp_file['size']>$this->_max_size){
                echo '你上传的文件过大';
                return false ;
            }
            if(!($tmp_file['error']===0)){
                echo '上传文件有误';
                return false ;
            }
            //增加一段代码，用来校验上传的文件类型是否正确
            //上传文件的后缀统一转成小写
            $ext = strtolower(strrchr($tmp_file['name'],'.'));

            if(!in_array($ext, $this->_ext_list)){
                echo '你上传的文件类型不对';
                return false;
            }
            //对文件进行第二级防护，对上传文件的MIME进行验证
            $mime_type =$tmp_file['type'];
            if(!in_array($mime_type, $this->_allow_mine_list)){
                echo '你上传的文件的mime不对';
                return false;
            }
            //对文件类型进行第三级防护，使用PHP程序对文件类型进行MIME检测
            //为了使用Finfo这个类，需要开启php.ini中一个扩展：extension php_fileinfo.dll
            $finfo = new Finfo(FILEINFO_MIME_TYPE);
            $mime_type=$finfo->file($tmp_file['tmp_name']);
            if (!in_array($mime_type, $this->_allow_mine_list)){
                echo '类型不合法';
                return false;
            }
            //这里我们增加一段代码，让文件名唯一
            $filename = uniqid($this->_prefix,true);
            //拼接一个完整唯一的文件名
            $upload_filename=$filename.$ext;

            //增加分目录存放处理，记得在最后带上/
            $sub_dir = date('Ymd').'/';
            //判断这个目录是否存在
            if (!is_dir($this->_upload_path.$sub_dir)){
                //如果目录不存在，则创建一个新的
                mkdir($this->_upload_path.$sub_dir,0777,true);
            }
            if (move_uploaded_file(iconv('gbk','utf-8',$tmp_file['tmp_name']), iconv('utf-8','gbk',$this->_upload_path.$sub_dir.$upload_filename))){
                return $sub_dir.$upload_filename;
            }else{
                return false;
            }
        }
    }