Default charset doesn't work with PHP MySQLi extension

Some charset change in MariaDB 11.3.1 appears to break PHP clients, raising the error 'Server sent charset (0) unknown to the client'.

I noticed /etc/mysql/mariadb.conf.d/50-server.cnf changed
collation-server = utf8mb4_general_ci (11.2.2)
to
character-set-collations = utf8mb4=uca1400_ai_ci (11.3.1)

If I change this back, connections from PHP work again.

This Plesk user seems to have encountered the same issue: https://talk.plesk.com/threads/500-plesk-exception-database-db-query-failed-sqlstate-hy000-2054-server-sent-charset-0-unknown-to-the-client.372563/

Steps to reproduce:

• Install PHP 8.3, including MySQLi extension.
• Install MariaDB 11.3.1, CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';.
• Test a PHP page, e.g.

  <?php

  error_reporting(E_ALL);

  ini_set('display_errors', 'on');

  $conn = new mysqli("localhost", "username", "password");

  if ($conn->connect_error) {

  die("Connection failed: " . $conn->connect_error);

  }

  echo "Connected successfully";

  ?>

• Observe error:

  Fatal error: Uncaught mysqli_sql_exception: Server sent charset (0) unknown to the client. Please, report to the developers in /var/www/html/index.php:4 Stack trace: #0 /var/www/html/index.php(4): mysqli->__construct() #1 {main} thrown in /var/www/html/index.php on line 4