How do you connect to MySQL using PHP's mysqli

I'm using MySQL 5.7.24 and PHP 7.2.10. MySQL is configured with SSL. I have a user my_user with password abc123. I have tried configuring with both authentication plugins:

ALTER USER 'my_user'@'192.168.192.150' IDENTIFIED WITH sha256_password BY 'abc123';
ALTER USER 'my_user'@'192.168.192.150' IDENTIFIED WITH mysql_native_password BY 'abc123';

From my PHP server, I can successfully connect using the mysql command line client without specifying anything other than the host, user, and password. However, from PHP, I can connect only when using mysql_native_password. Not when using sha256_password.

The following PHP code works fine with mysql_native_password:

$mysqli = mysqli_init();
$mysqli->options(MYSQLI_OPT_CONNECT_TIMEOUT, 5);

$con = $mysqli->real_connect('192.168.192.100', 'my_user', 'abc123', 'my_db', 
3306, null, MYSQLI_CLIENT_SSL | MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT);
var_dump($mysqli->query('SELECT 1;'));

However, when I use sha256_password, I get the error "Access denied for user 'my_user'@'192.168.192.150' (using password: YES)." I've tried alternately adding both of the following statements (before real_connect) with no success (but, I would add, I shouldn't need either of these, since I can connect with the command line client without specifying these options*).

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

So how is one supposed to use sha256_password from mysqli in PHP?

*NOTE: My PHP server is a different machine than my MySQL server. There is no my.cnf on the PHP that server that contains the ssl-ca, ssl-cert, and ssl-key options, so I really, try can connect without them using mysql.

UPDATE 1

In case it's helpful, here's some diagnostic info from phpinfo:

mysqli

MysqlI Support => enabled
Client API library version => mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $
Active Persistent Links => 0
Inactive Persistent Links => 0
Active Links => 0

Directive => Local Value => Master Value
mysqli.allow_local_infile => On => On
mysqli.allow_persistent => On => On
mysqli.default_host => no value => no value
mysqli.default_port => 3306 => 3306
mysqli.default_pw => no value => no value
mysqli.default_socket => no value => no value
mysqli.default_user => no value => no value
mysqli.max_links => Unlimited => Unlimited
mysqli.max_persistent => Unlimited => Unlimited
mysqli.reconnect => Off => Off
mysqli.rollback_on_cached_plink => Off => Off

mysqlnd

mysqlnd => enabled
Version => mysqlnd 5.0.12-dev - 20150407 - $Id: 38fea24f2847fa7519001be390c98ae0acafe387 $
Compression => supported
core SSL => supported
extended SSL => supported
Command buffer size => 4096
Read buffer size => 32768
Read timeout => 86400
Collecting statistics => Yes
Collecting memory statistics => No
Tracing => n/a
Loaded plugins => mysqlnd,debug_trace,auth_plugin_mysql_native_password,auth_plugin_mysql_clear_password,auth_plugin_caching_sha2_password,auth_plugin_sha256_password
API Extensions => mysqli,pdo_mysql

openssl

OpenSSL support => enabled
OpenSSL Library Version => OpenSSL 1.1.0g  2 Nov 2017
OpenSSL Header Version => OpenSSL 1.1.0g  2 Nov 2017
Openssl default config => /usr/lib/ssl/openssl.cnf

Directive => Local Value => Master Value
openssl.cafile => no value => no value
openssl.capath => no value => no value

For what I understand from documentation, only one auth_option can be active at a time.

So when your are doing

ALTER USER 'my_user'@'192.168.192.150' IDENTIFIED WITH sha256_password BY 'abc123';
ALTER USER 'my_user'@'192.168.192.150' IDENTIFIED WITH mysql_native_password BY 'abc123';

your second resquest actually redefines sha256_password auth to mysql_native_password