$bk = new Dbbackup();
$bk->path = "backup/";                           //SQL文件保存路径,默认为/backup
$bk->database='dbname';                                         //所要备份的数据库的名称
$bk->size='100';                                             //分卷分件大小
$bk->ileName='abc.sql';                                         //SQL文件名         
$bk->ds = "\n";                                        //换行符
$bk->sqlEnd = ";";                                     //每条SQL语句的结尾符号
$bk ->backup();应该是这样吧,但是没有连接帐号密码什么的啊