iconv()

(PHP 4 >= 4.0.5, PHP 5, PHP 7)

字符串按要求的字符编码来转换

说明

将字符串$str从$in_charset转换编码到$out_charset。

参数

输入的字符集。

输出的字符集。

如果你在$out_charset后添加了字符串//TRANSLIT，将启用转写（transliteration）功能。这个意思是，当一个字符不能被目标字符集所表示时，它可以通过一个或多个形似的字符来近似表达。如果你添加了字符串//IGNORE，不能以目标字符集表达的字符将被默默丢弃。否则，会导致一个E_NOTICE并返回FALSE。

//TRANSLIT运行细节高度依赖于系统的 iconv()实现（参见ICONV_IMPL）。据悉，某些系统上的实现会直接忽略//TRANSLIT，所以转换也有可能失败，$out_charset会是不合格的。

要转换的字符串。

返回值

返回转换后的字符串，或者在失败时返回FALSE。

更新日志

范例

iconv()例子

以上例程的输出类似于：

Original : This is the Euro symbol '€'.
TRANSLIT : This is the Euro symbol 'EUR'.
IGNORE   : This is the Euro symbol ''.
Plain    :
Notice: iconv(): Detected an illegal character in input string in .\iconv-example.php on line 7

The "//ignore" option doesn't work with recent versions of the iconv library. So if you're having trouble with that option, you aren't alone. 
That means you can't currently use this function to filter invalid characters. Instead it silently fails and returns an empty string (or you'll get a notice but only if you have E_NOTICE enabled).
This has been a known bug with a known solution for at least since 2009 years but no one seems to be willing to fix it (PHP must pass the -c option to iconv). It's still broken as of the latest release 5.4.3. 
https://bugs.php.net/bug.php?id=48147
https://bugs.php.net/bug.php?id=52211
https://bugs.php.net/bug.php?id=61484
[UPDATE 15-JUN-2012]
Here's a workaround...
 ini_set('mbstring.substitute_character', "none");
 $text= mb_convert_encoding($text, 'UTF-8', 'UTF-8');
That will strip invalid characters from UTF-8 strings (so that you can insert it into a database, etc.). Instead of "none" you can also use the value 32 if you want it to insert spaces in place of the invalid characters.

Please note that iconv('UTF-8', 'ASCII//TRANSLIT', ...) doesn't work properly when locale category LC_CTYPE is set to C or POSIX. You must choose another locale otherwise all non-ASCII characters will be replaced with question marks. This is at least true with glibc 2.5.
Example: 

Interestingly, setting different target locales results in different, yet appropriate, transliterations. For example: 

to test different combinations of convertions between charsets (when we don't know the source charset and what is the convenient destination charset) this is an example :

then after displaying, you use the $i$j that shows good displaying.
NB: you can add other charsets to $tab to test other cases.

If you are getting question-marks in your iconv output when transliterating, be sure to 'setlocale' to something your system supports.
Some PHP CMS's will default setlocale to 'C', this can be a problem.
use the "locale" command to find out a list..
$ locale -a
C
en_AU.utf8
POSIX

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