"Consistently utilizing UTF-8 encoding"

Question

I'm setting up a new server and want full UTF-8 support in my web application. I've tried this before on existing servers but always had to fall back to ISO-8859-1.

Where do I need to set the encoding/charset? I know I need to configure Apache, MySQL and PHP to achieve this - is there some standard checklist I can follow, or where mismatches can be ruled out?

This is a new Linux server running MySQL 5, PHP 5 and Apache 2.

Answer 1

I would like to add something to chazomaticus' excellent answer:

Also don't forget the META tag (like this, or HTML4 or XHTML version):

<meta charset="utf-8">

This may seem trivial, but IE7 gave me problems before.

I'm doing everything correctly; the database, database connection, and Content-Type HTTP headers are all set to UTF-8, which works fine in all other browsers, but Internet Explorer still insists on using the "Western European" encoding.

It turns out that the page is missing the META tag. After adding it, the problem was solved.

edit:

The W3C actually has a rather large section dedicated to I18N. They have a number of articles related to this issue - describing aspects of HTTP, (X)HTML and CSS:

• FAQ: Change (X)HTML page encoding to UTF-8
• Declare character encoding in HTML
• Tutorial: Character Sets and Encodings in XHTML, HTML and CSS
• Set HTTP character set parameters

They recommend using both HTTP headers and HTML meta tags (or XML declarations in the case of XHTML provided as XML).

Answer 2

data storage:

• Specify the utf8mb4 character set on all tables and text columns in the database. This allows MySQL to physically store and retrieve values ​​encoded in UTF-8. Note that if a utf8mb4_* collation is specified (without an explicit character set), MySQL will implicitly use the utf8mb4 encoding.

• In older versions of MySQL (utf8 which only supports a subset of Unicode characters. I wish I was kidding.

data access:

• In application code (such as PHP), no matter what database access method you use, you need to set the connection character set to utf8mb4. This way, MySQL doesn't do any conversion to its native UTF-8 when it passes the data to the application or vice versa.

• Some drivers provide their own mechanism to configure the connection character set, which both updates its own internal state and notifies MySQL to use the encoding on the connection - this is usually the preferred approach. In PHP:

  • If you are using the PDO abstraction layer for PHP ≥ 5.3.6, you can specify the charset in the DSN:

    $dbh = new PDO('mysql:charset=utf8mb4');

  • If you use mysqli, you can call set_charset():

    $mysqli->set_charset('utf8mb4');       // 面向对象风格
      mysqli_set_charset($link, 'utf8mb4');  // 过程化风格

  • If you can only use pure mysql, but happen to be running PHP ≥ 5.2.3, you can call mysql_set_charset.

• If the driver does not provide its own mechanism for setting the connection character set, you may need to issue a query to tell the MySQL application how you want the data on the connection to be encoded: SET NAMES 'utf8mb4 '.

• Same considerations as above regarding utf8mb4/utf8.

Output:

• UTF-8 should be set in the HTTP header, for example Content-Type: text/html; charset=utf-8. You can do this by setting default_charset (preferred) in php.ini or manually using the header() function.
• If your application transmits text to other systems, they also need to be told the character encoding. For web applications, the browser must be told the encoding in which the data is sent (via HTTP response headers or HTML metadata).
• When using json_encode() to encode the output, add JSON_UNESCAPED_UNICODE as the second parameter.

enter:

• The browser will submit the data in the character set specified by the document, so no special handling is required on input.
• If you have doubts about the request encoding (e.g. it may have been tampered with), you can verify that each received string is valid UTF-8 before trying to store or use it anywhere. PHP's mb_check_encoding() can do this, but you have to be strict about using it. There is really no way around this problem, as a malicious client can submit data in any encoding they want, and I haven't found a way to reliably get PHP to do this for you.

Other code notes:

• Obviously, all files you will provide (PHP, HTML, JavaScript, etc.) should be encoded in valid UTF-8.

• You need to make sure you do it safely every time you handle UTF-8 strings. This is the very difficult part. You may need to make extensive use of PHP's mbstring extension.

• PHP's built-in string operations are not UTF-8 safe by default. You can safely perform some operations using normal PHP string operations such as concatenation, but for most operations you should use the equivalent mbstring functions.

• To understand what you're doing (ie: don't screw it up), you really need to understand UTF-8 and how it works at the lowest level. Check out any of the links at utf8.com for great resources on everything you need to learn.