idn_to_utf8

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

idn_to_utf8 — Convert domain name from IDNA ASCII to Unicode

Description

Procedural style

idn_to_utf8(
    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 from an IDNA ASCII-compatible format to plain Unicode, encoded in UTF-8.

Parameters

domain: Domain to convert in an IDNA ASCII-compatible format.
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 in Unicode, encoded in UTF-8, 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_utf8() example

<?php

echo idn_to_utf8('xn--tst-qla.de'); 

?>

The above example will output:

täst.de

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User Contributed Notes 1 note

down

kushik.com ¶

11 years ago

<?php
// for those who has PHP older than version 5.3
class IDN {
    // adapt bias for punycode algorithm
    private static function punyAdapt(
        $delta,
        $numpoints,
        $firsttime
    ) {
        $delta = $firsttime ? $delta / 700 : $delta / 2; 
        $delta += $delta / $numpoints;
        for ($k = 0; $delta > 455; $k += 36)
            $delta = intval($delta / 35);
        return $k + (36 * $delta) / ($delta + 38);
    }
 
    // translate character to punycode number
    private static function decodeDigit($cp) {
        $cp = strtolower($cp);
        if ($cp >= 'a' && $cp <= 'z')
            return ord($cp) - ord('a');
        elseif ($cp >= '0' && $cp <= '9')
            return ord($cp) - ord('0')+26;
    }
 
    // make utf8 string from unicode codepoint number
    private static function utf8($cp) {
        if ($cp < 128) return chr($cp);
        if ($cp < 2048) 
            return chr(192+($cp >> 6)).chr(128+($cp & 63));
        if ($cp < 65536) return 
            chr(224+($cp >> 12)).
            chr(128+(($cp >> 6) & 63)).
            chr(128+($cp & 63));
        if ($cp < 2097152) return 
            chr(240+($cp >> 18)).
            chr(128+(($cp >> 12) & 63)).
            chr(128+(($cp >> 6) & 63)).
            chr(128+($cp & 63));
        // it should never get here 
    }
 
    // main decoding function
    private static function decodePart($input) {
        if (substr($input,0,4) != "xn--") // prefix check...
            return $input;
        $input = substr($input,4); // discard prefix
        $a = explode("-",$input);
        if (count($a) > 1) {
            $input = str_split(array_pop($a));
            $output = str_split(implode("-",$a));
        } else {
            $output = array();
            $input = str_split($input);
        }
        $n = 128; $i = 0; $bias = 72; // init punycode vars
        while (!empty($input)) {
            $oldi = $i;
            $w = 1;
            for ($k = 36;;$k += 36) {
                $digit = IDN::decodeDigit(array_shift($input));
                $i += $digit * $w;
                if ($k <= $bias) $t = 1;
                elseif ($k >= $bias + 26) $t = 26;
                else $t = $k - $bias;
                if ($digit < $t) break;
                $w *= intval(36 - $t);
            }
            $bias = IDN::punyAdapt(
                $i-$oldi,
                count($output)+1,
                $oldi == 0
            );
            $n += intval($i / (count($output) + 1));
            $i %= count($output) + 1;
            array_splice($output,$i,0,array(IDN::utf8($n)));
            $i++;
        }
        return implode("",$output);
    }
 
    public static function decodeIDN($name) {
        // split it, parse it and put it back together
        return 
            implode(
                ".",
                array_map("IDN::decodePart",explode(".",$name))
            );
    }
 
}
echo IDN::decodeIDN($_SERVER['HTTP_HOST']);
?>