/**
* ----------------------------------------------
* @example  A  object by yourself
* ----------------------------------------------
* $ftp = & discuz_ftp::instance();
* if(!$ftp->connect()) {
*     showmessage('FTP_ERR_'.$ftp->error());
* }
* $ftp->upload('/source/dir/file.name', 'target/dir/file.ext');
* if($ftp->error()) {
*     showmessage('ftp succeed upload');
* } else {
*     showmessage('FTP_ERR_'.$ftp->error());
* }
* $ftp->ftp_close();
* ----------------------------------------------
* @example  B  use function in function_core.php
* ----------------------------------------------
* $succeed = ftpcmd('upload', '/source/file.name');
* if(!$succeed) {
*     showmessage('FTP_ERR_'.ftpcmd('error));
* } else {
*     showmessage('ftp succeed upload');
* }
* ftpcmd('close');
*
*/