Full UTF-8

Question

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

Where exactly do I need to set the encoding/charset? I know I need to configure Apache, MySQL and PHP to do this - is there some standard checklist I can follow, or maybe troubleshoot where the mismatch occurs?

This applies to new Linux servers running MySQL 5, PHP, 5 and Apache 2.

P粉135292805 · Answer

I would like to add one thing to chazomaticus' excellent answer:

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

This may seem trivial, but IE7 has given me problems before.

I'm doing everything correct; 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. Adding it solves the problem.

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:

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

P粉536909186 · Answer

data storage:

Specify the utf8mb4 character set for all tables and text columns in the database. This allows MySQL to physically store and retrieve values natively encoded in UTF-8. Note that if the utf8mb4_* collation is specified (without any explicit character set), MySQL will implicitly use the utf8mb4 encoding.
In older versions of MySQL (< 5.5.3), you will unfortunately be forced to only use < 5.5.3) 中，不幸的是，您将被迫仅使用 utf8, which only supports a subset of Unicode characters. I wish I was kidding.

data access:

In your application code (such as PHP), regardless of which database access method you use, you need to set the connection character set to utf8mb4. This way, when MySQL passes data to your application, it doesn't convert from its native UTF-8 or vice versa.
Some drivers provide their own mechanism for configuring the connection character set, which both updates its own internal state and informs MySQL of the encoding to use 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 do this in DSN:
```
$dbh = new PDO('mysql:charset=utf8mb4');
```
- If you use mysqli, you can call set_charset():
```
$mysqli->set_charset('utf8mb4');       // object oriented style
  mysqli_set_charset($link, 'utf8mb4');  // procedural style
```
- If you insist on using plain 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 to set the connection character set, you may have to issue a query to tell MySQL how your application expects the data on the connection to be encoded: SET NAME 'utf8mb4 '. 

The same considerations apply for utf8mb4/utf8, as described above.


Output:

 UTF-8 should be set in the HTTP header, such as Content-Type: text/html; character set = utf-8. You can do this by setting default_charset in php.ini (preferred), or manually using the header() function. 

 If your application transfers text to other systems, they also need to know the character encoding. For web applications, the browser must be told the encoding in which to send the data (via HTTP response headers or HTML metadata). < /里>
When using json_encode() to encode the output, add JSON_UNESCAPED_UNICODE as the second parameter. 

enter:

 The browser will submit data for the character set specified by the document, so no special manipulation of the input is required. 
 If you have doubts about the request encoding (in case it might 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() does the following: Trick, but you have to use it religiously. There's really no way around this, as a malicious client can submit data in any encoding they want, and I haven't found a trick to get PHP to reliably do this for you. 

Other code notes:

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

You need to make sure that every time you handle a UTF-8 string, it is safe. Unfortunately, this is the hardest part. You may want to make extensive use of PHP's mbstring  extension. 

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

To know what you're doing (read: not screw it up), you really need to understand UTF-8 and how it works at the lowest level possible. Check out any of the links in utf8.com for some great resources on everything you need to know.

Full UTF-8

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