Character encodings work with PHP: 
ISO-8859-*, EUC-JP, UTF-8


Character encodings do NOT work with PHP:
JIS, SJIS

Character encoding, that does not work with PHP, may be converted with mbstring's HTTP input/output conversion feature/function.

Note: SJIS should not be used for internal encoding unless the reader is familiar with parser/compiler, character encoding and character encoding issues.

Note: If you use database with PHP, it is recommended that you use the same character encoding for both database and internal encoding for ease of use and better performance.

If you are using PostgreSQL, it supports character encoding that is different from backend character encoding. See the PostgreSQL manual for details.

How to Enable mbstring

mbstring is an extended module. You must enable module with configure script. Refer to the Install section for details.

The following configure options are related to mbstring module.

• --enable-mbstring : Enable mbstring functions. This option is required to use mbstring functions.

• --enable-mbstr-enc-trans : Enable HTTP input character encoding conversion using mbstring conversion engine. If this feature is enabled, HTTP input character encoding may be converted to mbstring.internal_encoding automatically.

HTTP Input and Output

HTTP input/output character encoding conversion may convert binary data also. Users are supposed to control character encoding conversion if binary data is used for HTTP input/output.

If enctype for HTML form is set to multipart/form-data, mbstring does not convert character encoding in POST data. If it is the case, strings are needed to be converted to internal character encoding.

• HTTP Input

  There is no way to control HTTP input character conversion from PHP script. To disable HTTP input character conversion, it has to be done in php.ini.

  Example 1. Disable HTTP input conversion in php.ini ;; Disable HTTP Input conversion mbstring.http_input = pass

  When using PHP as an Apache module, it is possible to override PHP ini setting per Virtual Host in httpd.conf or per directory with .htaccess. Refer to the Configuration section and Apache Manual for details.

• HTTP Output

  There are several ways to enable output character encoding conversion. One is using php.ini, another is using ob_start() with mb_output_handler() as ob_start callback function.

  Note: For PHP3-i18n users, mbstring's output conversion differs from PHP3-i18n. Character encoding is converted using output buffer.

;; Enable output character encoding conversion for all PHP pages

;; Enable Output Buffering
output_buffering    = On

;; Set mb_output_handler to enable output conversion
output_handler      = mb_output_handler

<?php

// Enable output character encoding conversion only for this page

// Set HTTP output character encoding to SJIS
mb_http_output('SJIS');

// Start buffering and specify "mb_output_handler" as
// callback function
ob_start('mb_output_handler');

?>

Supported Character Encoding

Currently, the following character encoding is supported by mbstring module. Caracter encoding may be specified for mbstring functions' encoding parameter.

The following character encoding is supported in this PHP extension :

UCS-4, UCS-4BE, UCS-4LE, UCS-2, UCS-2BE, UCS-2LE, UTF-32, UTF-32BE, UTF-32LE, UCS-2LE, UTF-16, UTF-16BE, UTF-16LE, UTF-8, UTF-7, ASCII, EUC-JP, SJIS, eucJP-win, SJIS-win, ISO-2022-JP, JIS, ISO-8859-1, ISO-8859-2, ISO-8859-3, ISO-8859-4, ISO-8859-5, ISO-8859-6, ISO-8859-7, ISO-8859-8, ISO-8859-9, ISO-8859-10, ISO-8859-13, ISO-8859-14, ISO-8859-15, byte2be, byte2le, byte4be, byte4le, BASE64, 7bit, 8bit and UTF7-IMAP.

php.ini entry, which accepts encoding name, accepts "auto" and "pass" also. mbstring functions, which accepts encoding name, and accepts "auto".

If "pass" is set, no character encoding conversion is performed.

If "auto" is set, it is expanded to "ASCII,JIS,UTF-8,EUC-JP,SJIS".

See also mb_detect_order()

Note: "Supported character encoding" does not mean that it works as internal character code.

php.ini settings

• mbstring.internal_encoding defines default internal character encoding.

• mbstring.http_input defines default HTTP input character encoding.

• mbstring.http_output defines default HTTP output character encoding.

• mbstring.detect_order defines default character code detection order. See also mb_detect_order().

• mbstring.substitute_character defines character to substitute for invalid character encoding.

Web Browsers are supposed to use the same character encoding when submitting form. However, browsers may not use the same character encoding. See mb_http_input() to detect character encoding used by browsers.

If enctype is set to multipart/form-data in HTML forms, mbstring does not convert character encoding in POST data. The user must convert them in the script, if conversion is needed.

Although, browsers are smart enough to detect character encoding in HTML. charset is better to be set in HTTP header. Change default_charset according to character encoding.

;; Set default internal encoding
;; Note: Make sure to use character encoding works with PHP
mbstring.internal_encoding    = UTF-8  ; Set internal encoding to UTF-8

;; Set default HTTP input character encoding
;; Note: Script cannot change http_input setting.
mbstring.http_input           = pass    ; No conversion. 
mbstring.http_input           = auto    ; Set HTTP input to auto
                                ; "auto" is expanded to "ASCII,JIS,UTF-8,EUC-JP,SJIS"
mbstring.http_input           = SJIS    ; Set HTTP2 input to  SJIS
mbstring.http_input           = UTF-8,SJIS,EUC-JP ; Specify order

;; Set default HTTP output character encoding 
mbstring.http_output          = pass    ; No conversion
mbstring.http_output          = UTF-8   ; Set HTTP output encoding to UTF-8

;; Set default character encoding detection order
mbstring.detect_order         = auto    ; Set detect order to auto
mbstring.detect_order         = ASCII,JIS,UTF-8,SJIS,EUC-JP ; Specify order

;; Set default substitute character
mbstring.substitute_character = 12307   ; Specify Unicode value
mbstring.substitute_character = none    ; Do not print character
mbstring.substitute_character = long    ; Long Example: U+3000,JIS+7E7E

;; Disable Output Buffering
output_buffering      = Off

;; Set HTTP header charset
default_charset       = EUC-JP    

;; Set HTTP input encoding conversion to auto
mbstring.http_input   = auto 

;; Convert HTTP output to EUC-JP
mbstring.http_output  = EUC-JP    

;; Set internal encoding to EUC-JP
mbstring.internal_encoding = EUC-JP    

;; Do not print invalid characters
mbstring.substitute_character = none

;; Enable Output Buffering
output_buffering     = On

;; Set mb_output_handler to enable output conversion
output_handler       = mb_output_handler

;; Set HTTP header charset
default_charset      = Shift_JIS

;; Set http input encoding conversion to auto
mbstring.http_input  = auto 

;; Convert to SJIS
mbstring.http_output = SJIS    

;; Set internal encoding to EUC-JP
mbstring.internal_encoding = EUC-JP    

;; Do not print invalid characters
mbstring.substitute_character = none

Basics for Japanese multi-byte character

Most Japanese characters need more than 1 byte per character. In addition, several character encoding schemas are used under a Japanese environment. There are EUC-JP, Shift_JIS(SJIS) and ISO-2022-JP(JIS) character encoding. As Unicode becomes popular, UTF-8 is used also. To develop Web applications for a Japanese environment, it is important to use the character set for the task in hand, whether HTTP input/output, RDBMS and E-mail.

• Storage for a character can be up to six bytes

• A multi-byte character is usually twice of the width compared to single-byte characters. Wider characters are called "zen-kaku" - meaning full width, narrower characters are called "han-kaku" - meaning half width. "zen-kaku" characters are usually fixed width.

• Some character encoding defines shift(escape) sequence for entering/exiting multi-byte character strings.

• ISO-2022-JP must be used for SMTP/NNTP.

• "i-mode" web site is supposed to use SJIS.

References

Multi-byte character encoding and its related issues are very complex. It is impossible to cover in sufficient detail here. Please refer to the following URLs and other resources for further readings.

• Unicode/UTF/UCS/etc

  http://www.unicode.org/

• Japanese/Korean/Chinese character information

  ftp://ftp.ora.com/pub/examples/nutshell/ujip/doc/cjk.inf

Table of Contents

mb_language --  Set/Get current language

mb_parse_str --  Parse GET/POST/COOKIE data and set global variable

mb_internal_encoding --  Set/Get internal character encoding

mb_http_input -- Detect HTTP input character encoding

mb_http_output -- Set/Get HTTP output character encoding

mb_detect_order --  Set/Get character encoding detection order

mb_substitute_character -- Set/Get substitution character

mb_output_handler --  Callback function converts character encoding in output buffer

mb_preferred_mime_name -- Get MIME charset string

mb_strlen -- Get string length

mb_strpos --  Find position of first occurrence of string in a string

mb_strrpos --  Find position of last occurrence of a string in a string

mb_substr -- Get part of string

mb_strcut -- Get part of string

mb_strwidth -- Return width of string

mb_strimwidth -- Get truncated string with specified width

mb_convert_encoding -- Convert character encoding

mb_detect_encoding -- Detect character encoding

mb_convert_kana --  Convert "kana" one from another ("zen-kaku" ,"han-kaku" and more)

mb_encode_mimeheader -- Encode string for MIME header

mb_decode_mimeheader -- Decode string in MIME header field

mb_convert_variables -- Convert character code in variable(s)

mb_encode_numericentity --  Encode character to HTML numeric string reference

mb_decode_numericentity --  Decode HTML numeric string reference to character

mb_send_mail --  Send encoded mail.

mb_get_info -- Get internal settings of mbstring