wp-config-sample.php should default to `utf8mb4` instead of `utf8` character set

[bchecketts]

MySQL's utf8 character encoding is not a correct implementation of the standard and doesn't work with 4-byte characters, which includes many emoji. utf8mb4 is the corrected implementation.

See ​https://medium.com/@adamhooper/in-mysql-never-use-utf8-use-utf8mb4-11761243e434 or just google "mysql utf8 vs utf8mb4"

It would seem wise for wp-config-sample.php to default then to utf8mb4 instead of utf8 so that new installations have the improved character set.

[SergeyBiryukov]

Previously: #21212, #32405, #33122.

Thanks for the ticket!

On both new and existing WordPress installs, WordPress will automatically upgrade the tables to utf8mb4 if the server supports that, and when DB_CHARSET is defined as utf8, it will automatically switch to utf8mb4 instead.

wp-config-sample.php still needs to default to utf8 though, as not all sites can support utf8mb4.