phpseclib 2.0.12 - SFTP login failed but no error - phpseclib

Question

I've installed phpseclib 2.0.12 with composer. I am running PHP 7.0.30.
I cannot log into an SFTP site using:
require($_SERVER["DOCUMENT_ROOT"] . "/vendor/autoload.php");
use phpseclib\Net\SFTP;
define('NET_SFTP_LOGGING', SFTP::LOG_COMPLEX);
$sftp = new SFTP($ftp_server);
echo("<pre>");
if (!$sftp->login($ftp_user_name, $ftp_user_pass)) {
print_r($sftp->getSFTPErrors());
echo $sftp->getSFTPLog();
exit('Login Failed');
} else {
echo("login worked");
}
echo("</pre>");
The output is simply:
Array
(
)
Login Failed
Why is logging not displaying anything at all? How can I see what is failing here?

Answer 1

You should be doing define('NET_SSH2_LOGGING', SSH2::LOG_COMPLEX); and $sftp->getLog(); instead. NET_SFTP_LOGGING only enables logging at the SFTP layer, which is only established after you've successfully authenticated.
Similarily, I'd do print_r($sftp->getErrors()); instead of print_r($sftp->getSFTPErrors());.

Answer 2

In case it helps someone else, I encountered a related issue and the password had a backslash in it. We changed our variable to use single quote marks instead of double and authentication worked. I suspect somewhere it was being treated as escape character. Perhaps this will helps someone save a few hours troubleshooting.