What do these PHP mbstring settings do?

Question

I'm trying to figure out exactly what these php.ini settings do. What happens when they're set to different values? When are they necessary? When are they harmful?

• mbstring.language
• mbstring.http_input
• mbstring.http_output
• mbstring.encoding_translation

As usual, the PHP manual is less than helpful.

EDIT: Just to clarify, I understand how character encodings work, and I understand how PHP's multi-byte functions differ from their single-byte counterparts. I'm looking for specifics on what the above settings do.

EDIT 2: OK, it looks like they actually do provide more documentation than just the page on runtime configuration, which just has one-line summaries. The first three of these are also functions, and there are more details on the pages that describe the function versions. I added links above.

Answer 1

You can change mbstring.language to whatever language you are using with. (Source)

language

; language for internal character representation.
mbstring.language = Neutral ; Set default language to neutral(UTF-8) (default)
mbstring.language = English
mbstring.language = Japanese
mbstring.language = Korean  ;For Korean market later

http_input

; http input encoding.
mbstring.http_input = pass
mbstring.http_input = auto
mbstring.http_input = UTF-8
mbstring.http_input = UTF-8, SJIS, EUC-JP

http_output

; http output encoding. mb_output_handler must be
; registered as output buffer to function
mbstring.http_output = pass
mbstring.http_output = UTF-8

encoding translation

; enable automatic encoding translation accoding to
; mbstring.internal_encoding setting. Input chars are
; converted to internal encoding by setting this to On.
; Note: Do _not_ use automatic encoding translation for
;       portable libs/applications.
mbstring.encoding_translation = On

Answer 2

The point is to support different character set encodings. There are a wide variety of encodings (ASCII, ANSI, UTF-8, etc) and each one has different character sets and number of bytes per character. The settings your looking at specify default encodings for different PHP functions.

PHP supplies a number of functions that help you deal with these different encodings properly. For an illustration, check out mb_strlen() vs strlen().

Short answer is, unless you're localizing your application's text, or communicating with systems with different encodings (your database included!), you probably don't need to worry about it.