Multibyte String Functions
Introduzione
While there are many languages in which every necessary character can be represented by a one-to-one mapping to an 8-bit value, there are also several languages which require so many characters for written communication that they cannot be contained within the range a mere byte can code (A byte is made up of eight bits. Each bit can contain only two distinct values, one or zero. Because of this, a byte can only represent 256 unique values (two to the power of eight)). Multibyte character encoding schemes were developed to express more than 256 characters in the regular bytewise coding system.
When you manipulate (trim, split, splice, etc.) strings encoded in a multibyte encoding, you need to use special functions since two or more consecutive bytes may represent a single character in such encoding schemes. Otherwise, if you apply a non-multibyte-aware string function to the string, it probably fails to detect the beginning or ending of the multibyte character and ends up with a corrupted garbage string that most likely loses its original meaning.
mbstring provides multibyte specific string functions that help you deal with multibyte encodings in PHP. In addition to that, mbstring handles character encoding conversion between the possible encoding pairs. mbstring is designed to handle Unicode-based encodings such as UTF-8 and UCS-2 and many single-byte encodings for convenience (listed below).
PHP Character Encoding Requirements
Encodings of the following types are safely used with PHP.
-
A singlebyte encoding,
- which has ASCII-compatible (ISO646 compatible) mappings for the characters in range of 00h to 7fh.
-
A multibyte encoding,
- which has ASCII-compatible mappings for the characters in range of 00h to 7fh.
- which don't use ISO2022 escape sequences.
- which don't use a value from 00h to 7fh in any of the compounded bytes that represents a single character.
These are examples of character encodings that are unlikely to work with PHP.
JIS, SJIS, ISO-2022-JP, BIG-5
Although PHP scripts written in any of those encodings might not work, especially in the case where encoded strings appear as identifiers or literals in the script, you can almost avoid using these encodings by setting up the mbstring's transparent encoding filter function for incoming HTTP queries.
Nota: It's highly discouraged to use SJIS, BIG5, CP936, CP949 and GB18030 for the internal encoding unless you are familiar with the parser, the scanner and the character encoding.
Nota: If you are connecting to a database with PHP, it is recommended that you use the same character encoding for both the database and the internal encoding for ease of use and better performance.
If you are using PostgreSQL, the character encoding used in the database and the one used in PHP may differ as it supports automatic character set conversion between the backend and the frontend.
Installazione
mbstring is a non-default extension. This means it is not enabled by default. You must explicitly enable the module with the configure option. See the Install section for details.
The following configure options are related to the mbstring module.
-
--enable-mbstring: Enable mbstring functions. This option is required to use mbstring functions.
libmbfl is necesarry for mbstring. libmbfl is bundled with mbstring. If libmbfl is already installed on the system, --with-libmbfl[=DIR] can be specified to use the installed library.
As of PHP 4.3.0, mbstring extension provides enhanced support for Simplified Chinese, Traditional Chinese, Korean, and Russian in addition to Japanese.
For PHP 4.3.3 or before, To enable that feature, you will have to supply either one of the following options to the LANG parameter of --enable-mbstring=LANG; --enable-mbstring=cn for Simplified Chinese support, --enable-mbstring=tw for Traditional Chinese support, --enable-mbstring=kr for Korean support, --enable-mbstring=ru for Russian support, and --enable-mbstring=ja for Japanese support (default). To enable all supported encoding, use --enable-mbstring=all.
Nota: As of PHP 4.3.4, all supported encoding by libmbfl is enabled with --enable-mbstring.
-
--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.
Nota: As of PHP 4.3.0, the option --enable-mbstr-enc-trans was eliminated and replaced with the runtime setting mbstring.encoding_translation. HTTP input character encoding conversion is enabled when this is set to On (the default is Off).
-
--disable-mbregex: Disable regular expression functions with multibyte character support.
Configurazione di Runtime
Il comportamento di queste funzioni è influenzato dalle impostazioni di php.ini.
| Name | Default | Changeable | Changelog |
|---|---|---|---|
| mbstring.language | "neutral" | PHP_INI_PERDIR | Available since PHP 4.3.0. |
| mbstring.detect_order | NULL | PHP_INI_ALL | Available since PHP 4.0.6. |
| mbstring.http_input | "pass" | PHP_INI_ALL | Available since PHP 4.0.6. |
| mbstring.http_output | "pass" | PHP_INI_ALL | Available since PHP 4.0.6. |
| mbstring.internal_encoding | NULL | PHP_INI_ALL | Available since PHP 4.0.6. |
| mbstring.script_encoding | NULL | PHP_INI_ALL | Available since PHP 4.3.0. |
| mbstring.substitute_character | NULL | PHP_INI_ALL | Available since PHP 4.0.6. |
| mbstring.func_overload | "0" | PHP_INI_PERDIR | PHP_INI_SYSTEM in PHP <= 4.2.3. Available since PHP 4.2.0. |
| mbstring.encoding_translation | "0" | PHP_INI_PERDIR | Available since PHP 4.3.0. |
| mbstring.strict_detection | "0" | PHP_INI_ALL | Available since PHP 5.1.2. |
Breve descrizione dei parametri di configurazione.
- mbstring.language string
-
The default national language setting (NLS) used in mbstring. Note that this option automagically defines mbstring.internal_encoding and mbstring.internal_encoding should be placed after mbstring.language in php.ini
- mbstring.encoding_translation boolean
-
Enables the transparent character encoding filter for the incoming HTTP queries, which performs detection and conversion of the input encoding to the internal character encoding.
- mbstring.internal_encoding string
-
Defines the default internal character encoding.
- mbstring.http_input string
-
Defines the default HTTP input character encoding.
- mbstring.http_output string
-
Defines the default HTTP output character encoding.
- mbstring.detect_order string
-
Defines default character code detection order. See also mb_detect_order().
- mbstring.substitute_character string
-
Defines character to substitute for invalid character encoding.
- mbstring.func_overload string
-
Overloads a set of single byte functions by the mbstring counterparts. See Function overloading for more information.
- mbstring.strict_detection boolean
-
Enables the strict encoding detection.
According to the » HTML 4.01 specification, Web browsers are allowed to encode a form being submitted with a character encoding different from the one used for the page. See mb_http_input() to detect character encoding used by browsers.
Although popular browsers are capable of giving a reasonably accurate guess to the character encoding of a given HTML document, it would be better to set the charset parameter in the Content-Type HTTP header to the appropriate value by header() or default_charset ini setting.
Example#1 php.ini setting examples
; Set default language
mbstring.language = Neutral; Set default language to Neutral(UTF-8) (default)
mbstring.language = English; Set default language to English
mbstring.language = Japanese; Set default language to Japanese
;; 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
;; HTTP input encoding translation is enabled.
mbstring.encoding_translation = On
;; 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
Example#2 php.ini setting for EUC-JP users
;; Disable Output Buffering output_buffering = Off ;; Set HTTP header charset default_charset = EUC-JP ;; Set default language to Japanese mbstring.language = Japanese ;; HTTP input encoding translation is enabled. mbstring.encoding_translation = On ;; 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
Example#3 php.ini setting for SJIS users
;; 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 default language to Japanese mbstring.language = Japanese ;; 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
Tipi di risorse
Questa estensione non definisce alcun tipo di risorsa.
Costanti predefinite
Queste costanti sono definite da questa estensione e sono disponibili solo se l'estensione è stata compilata nel PHP o se è stata caricata dinamicamente a runtime.