Description:
------------
According to the documentation, mysqli::$connect_error returns the last error message string from the last call to mysqli_connect(). NULL is returned if no error occurred.


However, if the underlying connection error is related to SSL, mysqli::$connect_error remains NULL which is incorrect.

The reproduction script tries to connect to a MySQL server running in a https://hub.docker.com/_/mysql container and relies on the fact that the CN in the autogenerated server certificate doesn't match its hostname.

The same problem is reproducible with literally any SSL error.

Test script:
---------------
<?php

$conn = mysqli_init();

$conn->ssl_set('client-key.pem', 'client-cert.pem', 'ca.pem', '', '');

if (!$conn->real_connect('127.0.0.1', 'root', '', 'mysql')) {
    var_dump($conn->connect_error);
    exit(1);
}


Expected result:
----------------
$conn->connect_error contains a string with an error message.

Actual result:
--------------
Warning: mysqli::real_connect(): Peer certificate CN=`MySQL_Server_8.0.18_Auto_Generated_Server_Certificate' did not match expected CN=`127.0.0.1' in /home/morozov/mysqi-tls.php on line 7

Warning: mysqli::real_connect(): Cannot connect to MySQL by using SSL in /home/morozov/mysqi-tls.php on line 7

Warning: mysqli::real_connect(): [2002]  (trying to connect via (null)) in /home/morozov/mysqi-tls.php on line 7

Warning: mysqli::real_connect(): (HY000/2002):  in /home/morozov/mysqi-tls.php on line 7
NULL