mb_language() sets language. If language is omitted, it returns current language as string.
language setting is used for encoding e-mail messages. Valid languages are "Japanese", "ja","English","en" and "uni" (UTF-8). mb_send_mail() uses this setting to encode e-mail.
Language and its setting is ISO-2022-JP/Base64 for Japanese, UTF-8/Base64 for uni, ISO-8859-1/quoted printable for English.
Return Value: If language is set and language is valid, it returns TRUE. Otherwise, it returns FALSE. When language is omitted, it returns language name as string. If no language is set previously, it returns FALSE.
See also mb_send_mail().