"Incorrect string value" errors with MySQL even with utf8mb4_unicode_ci

Question

My database stores server hostnames of Garry's Mod servers (Source Dedicated Servers) and sometimes they seem to contain characters that utf8mb4_unicode_ci can't store. What are these characters and how do I fix the issue?

insert into `servers` (`steamid64`, `script_id`, `ip_address`, `port`, `uses`, `hostname`, `maxplayers`, `map`, `last_active`) values (XXXXXXXXXXXXXXX, 1599, XXXXXXXXXXX, 27095, 1, [FR] USA vs F?d?ration | Apocalypse | SeriousRP | TSF, 20, rp_evocity_dc, CURRENT_TIMESTAMP())

Incorrect string value: '\xE9d\xE9rat...'

Illuminate\Database\QueryException: SQLSTATE[HY000]: General error: 1366 Incorrect string value: '\xE9d\xE9rat...' for column 'hostname' at row 1 (SQL: insert into `servers` (`steamid64`, `script_id`, `ip_address`, `port`, `uses`, `hostname`, `maxplayers`, `map`, `last_active`) values (XXXXXXXXXXXXXXX, 1599, XXXXXXXXXXXXXXXX, 27095, 1, [FR] USA vs F?d?ration | Apocalypse | SeriousRP | TSF, 20, rp_evocity_dc, CURRENT_TIMESTAMP()))
  File "app/Http/Controllers/PayloadController.php", line 243, in GetPayload
    $Server -> save();
  File "public/index.php", line 55
    $request = Illuminate\Http\Request::capture()

Answer 1

You were hoping for ...édérat... ?

Your client is using latin1, not utf8mb4.

Perhaps the simplest fix is to tell mysql that you are using latin1 in the client. This is best done in the connection string. (Are you using PDO or mysqli?)

Note: The encoding of the client and the encoding in the database table are independent. The transcoding is automatic. But you must be correct in declaring the encoding in the client.