ConFoo 2025

idn_to_ascii

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

idn_to_asciiConvert domain name to IDNA ASCII form

Description

Procedural style

idn_to_ascii(
    string $domain,
    int $flags = IDNA_DEFAULT,
    int $variant = INTL_IDNA_VARIANT_UTS46,
    array &$idna_info = null
): string|false

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

Parameters

domain

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

flags

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

variant

Either INTL_IDNA_VARIANT_2003 (deprecated as of PHP 7.2.0) for IDNA 2003 or INTL_IDNA_VARIANT_UTS46 (only available as of ICU 4.6) for UTS #46.

idna_info

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_*.

Return Values

The domain name encoded in ASCII-compatible form, or false on failure

Changelog

Version Description
7.4.0 The default value of variant is now INTL_IDNA_VARIANT_UTS46 instead of the deprecated INTL_IDNA_VARIANT_2003.
7.2.0 INTL_IDNA_VARIANT_2003 has been deprecated; use INTL_IDNA_VARIANT_UTS46 instead.

Examples

Example #1 idn_to_ascii() example

<?php

echo idn_to_ascii('täst.de');

?>

The above example will output:

xn--tst-qla.de

See Also

add a note

User Contributed Notes 4 notes

up
11
edible dot email at gmail dot com
12 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(cåsino.com) // is wrong

...whereas...

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.
up
7
mschrieck at gmail dot com
7 years ago
To convert IDN Domains with the IDNA2008 definition use following command.

idn_to_ascii('teßt.com',IDNA_NONTRANSITIONAL_TO_ASCII,INTL_IDNA_VARIANT_UTS46)

The result is then as expected

xn--tet-6ka.com
up
1
alexchexes at gmail dot com
1 year ago
idn_to_ascii and idn_to_utf8 functions don't properly handle full URLs (i.e. with schema and paths), so here's the helper functions which handles all URLs, including ones with path but without a scheme

<?php
/**
* Converts URLS to punycode
* It doesn't url-encodes other parts
* The initial code from snipp dor ru website, here is modified version that handles urls without scheme
*/
function punycode_encode($url)
{
$no_scheme = false;
if (!
preg_match('/^.+?:\/\//', $url) && substr($url, 0, 2) !== '//') {
$url = '//' . $url;
$no_scheme = true;
}

$parts = parse_url($url);

$out = '';
if (!empty(
$parts['scheme'])) $out .= $parts['scheme'] . ':';
if (!empty(
$parts['host'])) $out .= '//';
if (!empty(
$parts['user'])) $out .= $parts['user'];
if (!empty(
$parts['pass'])) $out .= ':' . $parts['pass'];
if (!empty(
$parts['user'])) $out .= '@';
if (!empty(
$parts['host'])) $out .= idn_to_ascii($parts['host']);
if (!empty(
$parts['port'])) $out .= ':' . $parts['port'];
if (!empty(
$parts['path'])) $out .= $parts['path'];
if (!empty(
$parts['query'])) $out .= '?' . $parts['query'];
if (!empty(
$parts['fragment'])) $out .= '#' . $parts['fragment'];

if (
$no_scheme) {
$out = substr($out, 2);
}

return
$out;
}

function
punycode_decode($url)
{
$no_scheme = false;
if (!
preg_match('/^.+?:\/\//', $url) && substr($url, 0, 2) !== '//') {
$url = '//' . $url;
$no_scheme = true;
}

$parts = parse_url($url);
$out = '';
if (!empty(
$parts['scheme'])) $out .= $parts['scheme'] . ':';
if (!empty(
$parts['host'])) $out .= '//';
if (!empty(
$parts['user'])) $out .= $parts['user'];
if (!empty(
$parts['pass'])) $out .= ':' . $parts['pass'];
if (!empty(
$parts['user'])) $out .= '@';
if (!empty(
$parts['host'])) $out .= idn_to_utf8($parts['host']);
if (!empty(
$parts['port'])) $out .= ':' . $parts['port'];
if (!empty(
$parts['path'])) $out .= $parts['path'];
if (!empty(
$parts['query'])) $out .= '?' . $parts['query'];
if (!empty(
$parts['fragment'])) $out .= '#' . $parts['fragment'];

if (
$no_scheme) {
$out = substr($out, 2);
}

return
$out;
}
up
0
mpf at mk dot de
1 year ago
The documentation ist not clear what failure in the return section means. This should be substituted to something like this:

"Returns failure if the given string could not be converted".
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