Bug #85946 MySQL 8.0.1 breaks php compatibilty

Description:
Running some tests of our PHP CLI application against MySQL 8.0 gives us the following error:

PHP Warning:  mysqli::__construct(): Server sent charset (255) unknown to the client. Please, report to the developers in /home/mysql/product/fromdual_brman-rev662/lib/fromdual_bman.inc on line 541
PHP Warning:  mysqli::__construct(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers in /home/mysql/product/fromdual_brman-rev662/lib/fromdual_bman.inc on line 541

How to repeat:
$mysqli = new mysqli($aConnection['host'], $aConnection['user'], $aConnection['password'], null, $aConnection['port'], null);
if ( $mysqli->connect_error ) {
  $rc = 175;
  $msg = $mysqli->connect_error . ' (' . $mysqli->connect_errno . ')' . " (rc=$rc).";
  tee('  ERROR: ' . $msg);
  return array($rc, null);
}

ii  libapache2-mod-php                              1:7.0+35ubuntu6                            all          server-side, HTML-embedded scripting language (Apache 2 module) (default)
ii  libapache2-mod-php7.0                           7.0.15-0ubuntu0.16.04.4                    amd64        server-side, HTML-embedded scripting language (Apache 2 module)
ii  php-common                                      1:35ubuntu6                                all          Common files for PHP packages
ii  php-mysql                                       1:7.0+35ubuntu6                            all          MySQL module for PHP [default]
ii  php7.0-cli                                      7.0.15-0ubuntu0.16.04.4                    amd64        command-line interpreter for the PHP scripting language
ii  php7.0-common                                   7.0.15-0ubuntu0.16.04.4                    amd64        documentation, examples and common module for PHP
ii  php7.0-json                                     7.0.15-0ubuntu0.16.04.4                    amd64        JSON module for PHP
ii  php7.0-mysql                                    7.0.15-0ubuntu0.16.04.4                    amd64        MySQL module for PHP
ii  php7.0-opcache                                  7.0.15-0ubuntu0.16.04.4                    amd64        Zend OpCache module for PHP
ii  php7.0-readline                                 7.0.15-0ubuntu0.16.04.4                    amd64        readline module for PHP

NAME="Ubuntu"
VERSION="16.04.2 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04.2 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
VERSION_CODENAME=xenial
UBUNTU_CODENAME=xenial

Suggested fix:
Do not break the protocols.

Works perfectly against MySQL 5.7 and MariaDB 10.2

oli, they changed the default charset now.   so you just have to put into my.cnf

[mysqld]
character-set-server=utf8

Hello Oli,

Thank you for the report.
Could you please confirm if you are still seeing the issue even after following Shane's suggestion?

Thanks,
Umesh

It seems like many clients will need to update to deal with this.

I submitted a PHP bug report:

https://bugs.php.net/bug.php?id=74461

Hello Umesh

Same issue:

oli@chef:/tmp [mysql-8.0.1, 3326]> ./insert_test.php 
PHP Warning:  mysqli::__construct(): Server sent charset (255) unknown to the client. Please, report to the developers in /tmp/insert_test.php on line 13
PHP Warning:  mysqli::__construct(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers in /tmp/insert_test.php on line 13
ERROR: Connect failed: (2054) Server sent charset unknown to the client. Please, report to the developers

root@mysql-8.0.1 [(none)] SQL> set global character_set_server='utf8';
Query OK, 0 rows affected (0.00 sec)

root@mysql-8.0.1 [(none)] SQL> show global variables like 'character_set_server';
+----------------------+-------+
| Variable_name        | Value |
+----------------------+-------+
| character_set_server | utf8  |
+----------------------+-------+
1 row in set (0.00 sec)

oli@chef:/tmp [mysql-8.0.1, 3326]> ./insert_test.php 
PHP Warning:  mysqli::__construct(): Server sent charset (255) unknown to the client. Please, report to the developers in /tmp/insert_test.php on line 13
PHP Warning:  mysqli::__construct(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers in /tmp/insert_test.php on line 13
ERROR: Connect failed: (2054) Server sent charset unknown to the client. Please, report to the developers

By the way, this still worked in 8.0.0 and was broken in 8.0.1.

Regards,
Oli

Oli, you really have to start the mysqld with the setting in my.cnf

[mysqld]
character-set-server=utf8

I am not sure why, to be honest.

Hello Shane

OK. Then it works...

root@localhost [(none)]> status;
--------------
mysql  Ver 8.0.1-dmr for linux-glibc2.12 on x86_64 (MySQL Community Server (GPL))

Connection id:          5
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         8.0.1-dmr-log MySQL Community Server (GPL)
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8
Db     characterset:    utf8
Client characterset:    utf8
Conn.  characterset:    utf8
UNIX socket:            /var/run/mysqld/mysql-3326.sock
Uptime:                 10 sec

root@localhost [(none)]> show global variables like 'character_set_server';
+----------------------+-------+
| Variable_name        | Value |
+----------------------+-------+
| character_set_server | utf8  |
+----------------------+-------+
1 row in set (0.00 sec)

root@localhost [(none)]> show global status like 'uptime';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Uptime        | 56    |
+---------------+-------+
1 row in set (0.01 sec)

mysql@chef:~/data/mysql-8.0 [mysql-8.0, 3326]> /tmp/insert_test.php 
connected
object(mysqli)#1 (19) {
  ["affected_rows"]=>
  int(0)
  ["client_info"]=>
  string(79) "mysqlnd 5.0.12-dev - 20150407 - $Id: b5c5906d452ec590732a93b051f3827e02749b83 $"
  ["client_version"]=>
  int(50012)
  ["connect_errno"]=>
  int(0)
  ["connect_error"]=>
  NULL
  ["errno"]=>
  int(0)
  ["error"]=>
  string(0) ""
  ["error_list"]=>
  array(0) {
  }
  ["field_count"]=>
  int(0)
  ["host_info"]=>
  string(20) "127.0.0.1 via TCP/IP"
  ["info"]=>
  NULL
  ["insert_id"]=>
  int(0)
  ["server_info"]=>
  string(13) "8.0.1-dmr-log"
  ["server_version"]=>
  int(80001)
  ["stat"]=>
  string(131) "Uptime: 90  Threads: 1  Questions: 13  Slow queries: 0  Opens: 176  Flush tables: 2  Open tables: 50  Queries per second avg: 0.144"
  ["sqlstate"]=>
  string(5) "00000"
  ["protocol_version"]=>
  int(10)
  ["thread_id"]=>
  int(6)
  ["warning_count"]=>
  int(0)
}

But this would lead to an other bug report?
SET GLOBAL character_set_server = 'utf8'; does not behave as it should???

Regards,
Oli

Thank you Oli for confirming that now it works per Shane's suggestions. 
For now I would mark this report as !bg as I see Bill K has opened bug @php which seems to be fixed as per updates in https://bugs.php.net/bug.php?id=74461

regards,
Umesh

Hello,
I have this problem with Matomo-platform.
So what is the practical/concrete solution?
Where should I change what: in Matomo? in MySQL? in PHP?
Friendly regards,
Rolf

Bug #93958 marked as duplicate of this one