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

idn_to_asciiConvert domain name to IDNA ASCII form.


Estilo procedural

string idn_to_ascii ( string $domain [, int $options = 0 [, int $variant = INTL_IDNA_VARIANT_2003 [, array &$idna_info ]]] )

This function converts a Unicode domain name to an IDNA ASCII-compatible format.



The domain to convert, which must be UTF-8 encoded.


Conversion options - combination of IDNA_* constants (except IDNA_ERROR_* constants).


Either INTL_IDNA_VARIANT_2003 for IDNA 2003 or INTL_IDNA_VARIANT_UTS46 for UTS #46.


This parameter can be used only if INTL_IDNA_VARIANT_UTS46 was used for variant. In that case, it will be filled with an array with the keys 'result', the possibly illegal result of the transformation, 'isTransitionalDifferent', a boolean indicating whether the usage of the transitional mechanisms of UTS #46 either has or would have changed the result and 'errors', which is an int representing a bitset of the error constants IDNA_ERROR_*.

Valor Retornado

The domain name encoded in ASCII-compatible form, ou FALSE em caso de falha


Versão Descrição
7.2.0 INTL_IDNA_VARIANT_2003 has been deprecated; use INTL_IDNA_VARIANT_UTS46 instead.
5.4.0/PECL 2.0.0b1 Added the parameters variant and idna_info; UTS #46 support.


Exemplo #1 idn_to_ascii() example


echo idn_to_ascii('tä'); 


O exemplo acima irá imprimir:

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  • idn_to_utf8() - Convert domain name from IDNA ASCII to Unicode.

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User Contributed Notes 1 note

edible dot email at gmail dot com
4 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.
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