Documentation

Introduction

The class idna_convert allows to convert internationalized domain names (see RFC 3490, 3491, 3492 and 3454 for details) as they can be used with various registries worldwide to be translated between their original (localized) form and their encoded form as it will be used in the DNS (Domain Name System).

The class provides two public methods, encode() and decode(), which do exactly what you would expect them to do. You are allowed to use complete domain names, simple strings and complete email addresses as well. That means, that you might use any of the following notations:

  • www.nörgler.com
  • xn--nrgler-wxa
  • xn--brse-5qa.xn--knrz-1ra.info

Errors, incorrectly encoded or invalid strings will lead to either a FALSE response (when in strict mode) or to only partially converted strings.
You can query the occurred error by calling the method getlasterror().

Unicode strings are expected to be either UTF-8 strings, UCS-4 strings or UCS-4 arrays. The default format is UTF-8. For setting different encodings, you can call the method setParams() - please see the inline documentation for details.
ACE strings (the Punycode form) are always 7bit ASCII strings.

ATTENTION: As of version 0.6.0 this class is written in the OOP style of PHP5. Since PHP4 is no longer actively maintained, you should switch to PHP5 as fast as possible. We expect to see no compatibility issues with the upcoming PHP6, too.

ATTENTION: BC break! As of version 0.6.4 the class per default allows the German ligature ß to be encoded as the DeNIC, the registry for .DE allows domains containing ß.
In older builds "ß" was mapped to "ss". Should you still need this behaviour, see example 5 below.

ATTENTION: As of version 0.8.0 the class fully supports IDNA 2008. Thus the aforementioned parameter is deprecated and replaced by a parameter to switch between the standards. See the updated example 5 below.

ATTENTION: BC break: As of version 1.0.0 the class closely follows the PSRs PSR-1, PSR-2 and PSR-4 of the PHP-FIG. As such the classes' naming has been changed, a namespace has been introduced and the default IDN version has changed from 2003 to 2008.

Examples

Example 1.

Say we wish to encode the domain name nörgler.com:

<?php
// Include the class
use Mso\IdnaConvert\IdnaConvert;
// Instantiate it
$IDN = new IdnaConvert();
// The input string, if input is not UTF-8 or UCS-4, it must be converted before
$input = utf8_encode('nörgler.com');
// Encode it to its punycode presentation
$output = $IDN->encode($input);
// Output, what we got now
echo $output; // This will read: xn--nrgler-wxa.com

Example 2.

We received an email from a punycoded domain and are willing to learn, how the domain name reads originally

<?php
// Include the class
use Mso\IdnaConvert\IdnaConvert;
// Instantiate it
$IDN = new IdnaConvert();
// The input string
$input = 'andre@xn--brse-5qa.xn--knrz-1ra.info';
// Encode it to its punycode presentation
$output = $IDN->decode($input);
// Output, what we got now, if output should be in a format different to UTF-8
// or UCS-4, you will have to convert it before outputting it
echo utf8_decode($output); // This will read: andre@börse.knörz.info

Example 3.

The input is read from a UCS-4 coded file and encoded line by line. By appending the optional second parameter we tell enode() about the input format to be used

<?php
// Include the class
use Mso\IdnaConvert\IdnaConvert;
// Instantiate it
$IDN = new IdnaConvert();
// Iterate through the input file line by line
foreach (file('ucs4-domains.txt') as $line) {
echo $IDN->encode(trim($line), 'ucs4_string');
echo "\n";
}

Example 4.

We wish to convert a whole URI into the IDNA form, but leave the path or query string component of it alone. Just using encode() would lead to mangled paths or query strings. Here the public method encode_uri() comes into play:

<?php
// Include the class
use Mso\IdnaConvert\IdnaConvert;
// Instantiate it
$IDN = new IdnaConvert();
// The input string, a whole URI in UTF-8 (!)
$input = 'http://nörgler:secret@nörgler.com/my_päth_is_not_ÄSCII/');
// Encode it to its punycode presentation
$output = $IDN->encodeUri($input);
// Output, what we got now
echo $output; // http://nörgler:secret@xn--nrgler-wxa.com/my_päth_is_not_ÄSCII/

Example 5.

Per default, the class converts strings according to IDNA version 2008. To support IDNA 2003, the class needs to be invoked with an additional parameter. This can also be achieved on an instance.

<?php
// Include the class
use Mso\IdnaConvert\IdnaConvert;
// Instantiate it, switching to IDNA 2003, the original, now outdated standard
$IDN = new IdnaConvert(['idn_version' => 2003]);
// Sth. containing the German letter ß
$input = 'meine-straße.de');
// Encode it to its punycode presentation
$output = $IDN->encode_uri($input);
// Output, what we got now
echo $output; // xn--meine-strae-46a.de
// Switch back to IDNA 2008
$IDN->setIdnVersion(2003);
// Sth. containing the German letter ß
$input = 'meine-straße.de');
// Encode it to its punycode presentation
$output = $IDN->encodeUri($input);
// Output, what we got now
echo $output; // meine-strasse.de

Encoding helper

In case you have strings in encodings other than ISO-8859-1 and UTF-8 you might need to translate these strings to UTF-8 before feeding the IDNA converter with it. PHP's built in functions utf8_encode() and utf8_decode() can only deal with ISO-8859-1.
Use the encoding helper class supplied with this pacagke for the conversion. It requires either iconv, libiconv or mbstring installed together with one of the relevant PHP extensions. The functions you will find useful are toUtf8() as a replacement for utf8_encode() and fromUtf8() as a replacement for utf8_decode().

Example usage:

<?php
use Mso\IdnaConvert\IdnaConvert;
use Mso\IdnaConvert\EncodingHelper;
$mystring = '<something in e.g. ISO-8859-15';
$mystring = EncodingHelper::toUtf8($mystring, 'ISO-8859-15');
$IDN = new IdnaConvert();
echo $IDN->encode($mystring);

UCTC — Unicode Transcoder

Another class you might find useful when dealing with one or more of the Unicode encoding flavours. It can transcode into each other: - UCS-4 string / array
- UTF-8
- UTF-7
- UTF-7 IMAP (modified UTF-7)
All encodings expect / return a string in the given format, with one major exception: UCS-4 array is just an array, where each value represents one code-point in the string, i.e. every value is a 32bit integer value.

Example usage:

<?php
use Mso\IdnaConvert\UnicodeTranscoder;
$mystring = 'nörgler.com';
echo UnicodeTranscoder::convert($mystring, 'utf8', 'utf7imap');