CI_FTP::mirror()

mirror($locpath, $rempath)

Recursively reads a local folder and everything it contains (including sub-folders) and creates a mirror via FTP based on it. Whatever the directory structure of the original file path will be recreated on the server. You must supply a source path and a destination path:

$this->ftp->mirror('/path/to/myfolder/', '/public_html/myfolder/');