How to set up Unicode

  1. 1. PHP script files
  2. 2. PHP-Code and Yii Application
  3. 3. Database
  4. 4. Database connection
  5. 5. HTTP Content-Type

To fix issues with display of special language characters once and for all there's a solution: use Unicode UTF-8 everywhere. If everything is set up to use Unicode, you can use mostly every language in your application.

Info: Strictly speaking, Unicode is a character set. It lists and names characters from every main language around the world. UTF-8 is an encoding. It defines a mapping between Unicode characters and a sequence of bytes. Other Unicode encodings exists, like UTF-16, but they are far less used on the web. UTF-8 has a main advantage over other Unicode encodings : it is backward compatible with ASCII.

There are several places that all may need some configuration tuning to use Unicode.

1. PHP script files

Every text file is stored in a specific character set on disk. For your PHP files this must be UTF-8 charset without BOM. Make sure to use an editor which is capable of Unicode. If you have some older non-unicode files in your project open them with your editor and save them again UTF-8 encoded.

Tip: On Windows you can for example use Notepad++, which has an Encoding menu from where you can change encodings of your files.

On Linux you can also use command line tools like recode or iconv to convert a whole bunch of files. Here's a script that converts every php file in the directory myproject/ and its sub-directories:

$ cd myproject/
$ for i in $(find -name '*.php'); do encoding=$(file -bi "$i" | sed -e 's/.*[ ]charset=//'); iconv -f $encoding -t UTF-8 -o "$i" "$i"; done

2. PHP-Code and Yii Application

PHP needs to use UTF-8 internally in order for e.g. string length validation to work correctly. Scripts should use mbstring functions instead of the non-multibyte aware counterparts.

By default, the Yii applications already supposes your character set to be UTF-8. See CApplication::charset. This is used for encoding text in HTML pages, e.g. by CHtml::encode().

Yii > 1.1.1

Yii will try to use mbstring functions if they are available. For the string validator you should set the encoding parameter to utf-8.

Older versions of Yii

A workaround for older releases is to use mbstring's function overloading feature. This will override then non-multibyte aware functions with their mbstring counterpart.

To set this up add this in your php.ini:

mbstring.func_overload "7"
mbstring.internal_encoding "UTF-8"

or configure it in a VirtualHost section in Apache:

php_admin_value mbstring.func_overload "7"
php_admin_value mbstring.internal_encoding "UTF-8"

>Note: Unfortunately it's not recommended to set this in an .htaccess file as this may lead to undefined behavior.

3. Database

Your database needs to know that it should store data in utf-8. The configuration for that might differ between database systems.


The charset can be defined per database and per table. Use the following SQL to find out the charset for an existing database or table:

SHOW CHARACTER SET FOR mydatabase.mytable;

Info: Don't confuse the encoding of characters in a table with its collation. The latter is used for sorting in queries and can be changed easily with e.g. phpMyAdmin or even for a single query.

If your table doesn't use UTF-8 charset yet the most reliable way to change this is to export your table, modify the CREATE statement's CHARSET parameter and re-import your table again into the database.

Be very careful when doing this conversion. You need to make sure you use the correct connection charset and save the file in UTF-8. If not performed carefully you can easily end up with messed up encodings, e.g. having ISO-8859-1 encoded characters in a table with utf8 CHARSET.

Tip: To have MySQL create all of your tables with utf8 charset and collation by default, you can add this to your MySQL configuration (e.g. my.cnf file):

>~~~ >[mysqld] >character_set_server = utf8 >collation_server = utf8_general_ci ># for older versions: >default-character-set = utf8 >~~~

4. Database connection

When connecting to a database a client like PHP also has to use a specific charset encoding. To specify the charset to use for a connection in Yii, configure it like this:

return array(
    // ...
    'components' => array(
        // ...
        'db' => array(
            // ..
            'charset' => 'utf8',

If you have problems with the charset configuration above you can also try to set the charset with a SQL command. You can use the initSQLs configuration:

        'initSQLs'=>'SET NAMES utf8 ;',

5. HTTP Content-Type

We also need to let the browser know, that we use UTF-8 with our pages. There are 2 options for this:

  • HTTP Content-Type header. This is configured in the webserver but can also be set from PHP (see below).
  • Content-Type meta tag. You could add a meta tag to your HTML pages like <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />.

The recommended way is to use the HTTP header as it overrides what you have set in the meta tag.

>Tip: If you let the webserver set the header, there's no need to add additional header information about encoding to your pages. In this case you would only have to overwrite the HTTP header if your page where not in UTF-8.


You can configure the Content-Type header either in a VirtualHost section of your server or in a .htaccess file in your DocumentRoot. Add this line:

AddDefaultCharset UTF-8

The right Content-Type header is set with this directive:

server {
   charset UTF-8;
PHP alternative

If you don't have access to or don't want to modify your server configuration you can also set the content type from PHP. Again you have different options:

  • Set default_charset to utf8 in your php.ini
  • Add the following PHP command to Yii's index.php: header('Content-Type: text/html; charset=utf-8');.

The drawback of this method is that it sets the header only for PHP files. So if you also serve some static content, it will not have the right Content-Type header set.

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Viewed: 136 296 times
Version: 1.1
Category: How-tos
Tags: i18n, unicode
Written by: Mike
Last updated by: Roman Solomatin
Created on: Feb 21, 2009
Last updated: 11 years ago
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