(PHP 5 >= 5.3.0, PHP 7, PHP 8, PECL intl >= 1.0.2, PECL idn >= 0.1)

idn_to_ascii将域名转换为 IDNA ASCII 格式



    string $domain,
    int $options = IDNA_DEFAULT,
    int $variant = INTL_IDNA_VARIANT_UTS46,
    array &$idna_info = ?
): string|false

该函数可以将 Unicode 域名转换为 IDNA ASCII 兼容格式。



要转换的域,必须使用 UTF-8 编码。


转换选项 — IDNA_* 开头的常量(除 IDNA_ERROR_* 开头的常量)。


对于 IDNA 2003 是 INTL_IDNA_VARIANT_2003 (自 PHP 7.2.0 起已弃用), 对于 UTS #46 是 INTL_IDNA_VARIANT_UTS46 (仅 ICU 4.6 起可用)。


仅当 INTL_IDNA_VARIANT_UTS46 用于 variant 时,才可以使用该参数。 在这种情况下,它将用这些键组成的数组来填充: 'result' 键,转换结果(有可能是一个非法结果); 'isTransitionalDifferent' 键,布尔值,指示使用 UTS #46 的过滤机制是否会改变结果; 'errors' 键,是 IDNA_ERROR_* 常量集里一个常量对应的 int


IDNA ASCII 兼容格式编码的域名, 或者在失败时返回 false


版本 说明
7.4.0 现在 variant 的默认值为 INTL_IDNA_VARIANT_UTS46 , 而不是已弃用的 INTL_IDNA_VARIANT_2003
7.2.0 INTL_IDNA_VARIANT_2003 已被弃用; 可以使用 INTL_IDNA_VARIANT_UTS46 代替。


示例 #1 idn_to_ascii() 示例


echo idn_to_ascii('tä'); 




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User Contributed Notes 3 notes

edible dot email at gmail dot com
10 years ago
The notes on this function are not very clear and a little misleading.

Firstly, <=5.3, you will need to make use of one of several scripts or classes available on the internet which might, or might not, require the installation of of the intl and idn PECL extensions ...and you will need to have !<4.0 in order to be able to install both.

Secondly, if you have >=5.4 you will not require the PECL extensions.

Third, use of utf8_encode() is not necessary.  In fact, it will potentially prevent idn_to_ascii() from working at all.

On my setup it was necessary to change the charset in the script meta tags to UTF-8:

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

...and to change charset_default in the php.ini file (/usr/local/lib/php.ini, whereis php.ini, find / -name php.ini):

default_charset = "UTF-8"

The above changes mean that idn_to_ascii() can now be used with that syntax (no need for utf8_encode()).  Previously, the function worked to convert some IDNs, but failed to convert Japanese and Cyrillic IDNs.  Further, no additional locales were enabled or added, and Apache's charset file was left unmodified.

It is also important to remember only to apply the function where required, eg:

idn_to_ascii(cå // is wrong


iden_to_ascii(cåsino) // is right

...and also be aware of text editors that don't support UTF-8 encoding, or the $domain = 'cåsino' value will end up as $domain = '??????' ...and the function will fail.

I have found that Notepad++ easily and reliably handles UTF-8 encoding that works for this function using UTF-8 as the encoding option, not UTF-8 without BOM.
mschrieck at gmail dot com
5 years ago
To convert IDN Domains with the IDNA2008 definition use following command.


The result is then as expected
waxblur at gmx dot at
2 years ago
In Windows, the path to the PHP folder must still be present in the PATH environment variable, becouse the necessary DLLs (icudt65.dll, icuin65.dll etc.) are available in this folder.
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