$fn = 'foo.bar';
$ftp_user = 'user@mydomain.com';
$ftp_pass = 'my-pass';
$ftp_host = 'ip.xx.xx.xx';
$ftp_uri = 'ftp://'.$ftp_user.':'.$ftp_pass.'@'.$ftp_host.'/home/user/public_html/test_dir/'.$fn;
$content = 'asdq3ersesdf';
$options = array('ftp' => array('overwrite' => true));
$stream = stream_context_create($options);
file_put_contents($ftp_uri, $content, 0, $stream);