Error when use do_upload - php

Question

I have a problem when I use do_upload its always returns an error saying 'The upload path does not appear to be valid'.
function save_blog(){
$config['upload_path'] = 'ftp://username:password#hostname:port/public_html/img/blog/';
//$config['upload_path'] = 'img/blog/';
$config['allowed_types'] = 'gif|jpg|png';
get_instance()->load->library('upload', $this->config);
echo $config['upload_path'];
if($this->upload->do_upload('myDoc'))
{
echo "file upload success";
}
else
{
echo $this->upload->display_errors();
}
}
On my server there are path /public_html/img/blog/
PS* i can use do_upload when i used a simple code like http://ellislab.com/codeigniter/user-guide/libraries/file_uploading.html
but on my project I have to upload 2 files in one click so I try to use $this->upload->do_upload('myDoc') for one of my input first but it still error.

Answer 1

Updated:
If you need to upload files, do do_upload first by your first method to local folder, and then FTP upload the local file to FTP server.
I think if you need to upload via FTP. for establishing a valid connection to FTP.
http://ellislab.com/codeigniter/user-guide/libraries/ftp.html
Example for Codeigniter.
$this->load->library('ftp');
$config['hostname'] = 'ftp.example.com';
$config['username'] = 'your-username';
$config['password'] = 'your-password';
$config['debug'] = TRUE;
$this->ftp->connect($config);
$this->ftp->upload('/local/path/to/myfile.html', '/public_html/myfile.html', 'ascii', 0775);
$this->ftp->close();
Exmaple for PHP only. (Credits to http://www.jonasjohn.de/snippets/php/ftp-example.htm)
// FTP access parameters
$host = 'ftp.example.org';
$usr = 'example_user';
$pwd = 'example_password';
// file to move:
$local_file = './example.txt';
$ftp_path = '/data/example.txt';
// connect to FTP server (port 21)
$conn_id = ftp_connect($host, 21) or die ("Cannot connect to host");
// send access parameters
ftp_login($conn_id, $usr, $pwd) or die("Cannot login");
// turn on passive mode transfers (some servers need this)
// ftp_pasv ($conn_id, true);
// perform file upload
$upload = ftp_put($conn_id, $ftp_path, $local_file, FTP_ASCII);
// check upload status:
print (!$upload) ? 'Cannot upload' : 'Upload complete';
print "\n";
/*
** Chmod the file (just as example)
*/
// If you are using PHP4 then you need to use this code:
// (because the "ftp_chmod" command is just available in PHP5+)
if (!function_exists('ftp_chmod')) {
function ftp_chmod($ftp_stream, $mode, $filename){
return ftp_site($ftp_stream, sprintf('CHMOD %o %s', $mode, $filename));
}
}
// try to chmod the new file to 666 (writeable)
if (ftp_chmod($conn_id, 0666, $ftp_path) !== false) {
print $ftp_path . " chmoded successfully to 666\n";
} else {
print "could not chmod $file\n";
}
// close the FTP stream
ftp_close($conn_id);