utf8mb4character set on all tables and text columns in your database. This makes MySQL physically store and retrieve values encoded natively in UTF-8. Note that MySQL will implicitly use
utf8mb4encoding if a
utf8mb4_*collation is specified (without any explicit character set).
In older versions of MySQL (< 5.5.3), you’ll unfortunately be forced to use simply
utf8, which only supports a subset of Unicode characters. I wish I were kidding.
In your application code (e.g. PHP), in whatever DB access method you use, you’ll need to set the connection charset to
utf8mb4. This way, MySQL does no conversion from its native UTF-8 when it hands data off to your application and 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 be used on the connection—this is usually the preferred approach. In PHP:
If you’re using the PDO abstraction layer with PHP ≥ 5.3.6, you can specify
charsetin the DSN:
$dbh = new PDO('mysql:charset=utf8mb4');
If you’re using mysqli, you can call
$mysqli->set_charset('utf8mb4'); // object oriented style mysqli_set_charset($link, 'utf8mb4'); // procedural style
If you’re stuck with plain mysql but happen to be running PHP ≥ 5.2.3, you can call
If the driver does not provide its own mechanism for setting the connection character set, you may have to issue a query to tell MySQL how your application expects data on the connection to be encoded:
SET NAMES 'utf8mb4'.
The same consideration regarding
utf8applies as above.
- UTF-8 should be set in the HTTP header, such as
Content-Type: text/html; charset=utf-8. You can achieve that either by setting
default_charsetin php.ini (preferred), or manually using
- If your application transmits text to other systems, they will also need to be informed of the character encoding. With web applications, the browser must be informed of the encoding in which data is sent (through HTTP response headers or HTML metadata).
- When encoding the output using
JSON_UNESCAPED_UNICODEas a second parameter.
- Browsers will submit data in the character set specified for the document, hence nothing particular has to be done on the input.
- In case you have doubts about request encoding (in case it could be tampered with), you may verify every received string as being valid UTF-8 before you try to store it or use it anywhere. PHP’s
mb_check_encoding()does the trick, but you have to use it religiously. There’s really no way around this, as malicious clients can submit data in whatever encoding they want, and I haven’t found a trick to get PHP to do this for you reliably.
Other Code Considerations:
You need to make sure that every time you process a UTF-8 string, you do so safely. This is, unfortunately, the hard part. You’ll probably want to make extensive use of PHP’s
PHP’s built-in string operations are not by default UTF-8 safe. There are some things you can safely do with normal PHP string operations (like concatenation), but for most things you should use the equivalent
To know what you’re doing (read: not mess it up), you really need to know UTF-8 and how it works on the lowest possible level. Check out any of the links from utf8.com for some good resources to learn everything you need to know.