PHP Manual: Specify or get the character encoding in which the messages from the DOMAIN message catalog will be returned

stringfalse bind_textdomain_codeset(string $domain, stringnull $codeset)

bind_textdomain_codeset allows to set or get the encoding in which messages from domain will be returned by gettext and similar functions.

domain: The domain.
codeset: The code set. If null, the currently set encoding is returned.

A string on success.

Throws a ValueError if domain is the empty string.

Version	Description
8.4.0	Now throws a ValueError if `domain` is the empty string.
8.0.3	`codeset` is nullable now. Previously, it was not possible to retrieve the currently set encoding.

Note:
The bind_textdomain_codeset information is maintained per process, not per thread.