One of the biggest issues with the web is encoding.
In the old days the formerly base standard was ISO 8859-1, where there ware 191 latin characters defined, and 1 char = 1B. For different languages, different encodings ware used, but from here many portability issues appeared, the possibility to cover a greater number of languages etc.
The problem occurs when a project should be available in several languages, and the number of the languages is not controlled. A big project like WordPress for example should be available with any language.
Unicode is a better alternative for ISO 8859-1, having more then 100.000 characters defined. In other words it has about every character of about any existing language.
As I was saying for MySQL, UTF-8 characters have a variable length between 1 and 4B.
Displaying the UTF-8 content in PHP pages
For browser to interpret the page content as UTF-8, it should receive the right headers:
1<?php header("Content-type: text/html; charset=utf-8");?>
Attention! The header should be the first thing that is send from the server! In other words it should be the first thing displayed on the page.
The type of the document can be specified with the “Content-Type” meta tag. If there is a similar meta tag on the page it should be removed and replace with:
1<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
The .htaccess file and string processing
Add to the .htaccess file (for Apache servers) the following lines:
1# default charset used by PHP 2php_value default_charset utf-8 3# encoding for mbstring 4php_value mbstring.internal_encoding utf-8 5php_value mbstring.func_overload 7
The first line sets the default charset for PHP, this setting can be made directly to php.ini.
Second and third line sets the mbstring (multi byte string) functions.
Using UTF-8, as I was saying earlier, 1 char != 1B, so errors may appear:
1$var = 'aşadar'; 2 3echo strlen($var).PHP_EOL; // 7 4echo strtoupper($var).PHP_EOL; // AşADAR 5 6// using mbstring functions 7echo mb_strlen($var).PHP_EOL; // 6 8echo mb_strtoupper($var).PHP_EOL; // AŞADAR
This is why we set the mbstring functions mode using the .htaccess file. Content entered through forms should be processed using mbstring functions, to avoid problems like in the earlier example.
The available functions are in the manual.
Coding old content
There are many ways to encode ISO 8859-1 content to UTF-8. A couple of ways of doing that with PHP are:
– iconv() function which converts from a format to another specified format:
1echo iconv("ISO-8859-1", "UTF-8", "Test");
– utf8_encode() function which converts from ISO 8859-1 to UTF-8:
What does the future bring?
The long-expected PHP6 will have native support for Unicode, so all the above tricks will be unnecessary. At the moment of writing this blog PHP 6 is 70.70% done, and with a little luck it will be ready in less then an year.
Along with globalization, the old ASCII code is no longer suitable. Consider that one day you have to develop a project in German, Russian or even Japanese, you could adapt the charset for each of these languages or you could simply develop using Unicode.
To use Unicode with MySQL UTF-8 can be used.
You must note that UTF-8 characters are variable in length and they are ASCII compatible. In ASCII 1 char = 1B, in UTF-8 1 char can be between 1 and 4 B.
UTF-8 charset and collation on the server
Character type in MySQL is dictated by charset.
To check if UTF-8 in installed on the server:
1SHOW CHARSET LIKE 'utf8';
or with information_schema
1SELECT * FROM `CHARACTER_SETS` WHERE CHARACTER_SET_NAME = 'utf8';
If the charset was found then we can continue.
Another element that appears with charset is collation, which it’s used for comparing strings at ordering.
To see what collations are available on the server:
1SHOW COLLATION WHERE CHARSET = 'utf8';
or with information_schema
1SELECT * FROM `COLLATIONS` WHERE CHARACTER_SET_NAME = 'utf8';
Collation are usually by language, for comparing strings with or without diacritics for example, or “bin” can be used with orders strings in binary mode, ie “A” is greater than “a” for example.
If no collation is specified, then the default one will be used.
UTF-8 and data bases
When creating a database you can specify the default charset to be used with all new tables for which there isn’t any charset specified.
1CREATE DATABASE db_name CHARACTER SET utf8 COLLATE utf8_romanian_ci;
Or for modifying the default charset for a data base which already exists:
1ALTER DATABASE db_name CHARACTER SET utf8 COLLATE utf8_romanian_ci;
UTF-8, tables and columns
For modifying tables which already exist ALTER TABLE must be used is used.
A table can have a default charset and collation, and each column can have it’s own charset and collation.
For more information about the table:
1SHOW CREATE TABLE tab;
To set a charset for an existing table:
1ALTER TABLE tab CHARSET = utf8 COLLATE = utf8_romanian_ci;
For modifying the charset of a VARCHAR(200) column is used:
1ALTER TABLE tab MODIFY c1 VARCHAR(200) CHARSET utf8 COLLATE utf8_romanian_ci;
A “problem” that may arise is related to the size of the character, it’s size can be between 1 and 4B. That is why for measuring a string column (like varchar) you must use CHAR_LENGTH(str) instead of LENGTH().
A short exemple:
1SET @var = 'aşadar'; 2SELECT CHAR_LENGTH(@var) AS 'Char', LENGTH(@var) AS 'Length'; 3 4// The output is: Char = 6 and Length = 7 because ş is 2B