(PHP Extension) Punycode Encoding / Decoding

Punycode is an encoding standard for representing Unicode characters using only the 7bit us-ascii characters that are permitted in network host names. Punycode is used for internationalized domain names -- i.e. IDN or IDNA (Internationalizing Domain Names in Applications).

Punycode is defined in RFC 3492. Converting to/from punycode does not include the "xn--" prefix. The "xn--" prefix is to signify that punycode follows. For example, the string " café.com" is converted to "caf-dma.com" in punycode. The punycode domain name is "xn--caf-dma.com".

Converting an email address to punycode would be as follows. Suppose the email address is "coffee@café.com". The punycode representation is "coffee@xn--caf-dma.com". The RFC 3492 punycode representation of "café.com" is simply "caf-dma.com", but the punycode domain name is "xn--caf-dma.com".

The "xn--" is a constant. It is the same regardless of the domain. For example, the punycode URL representation of "mañana.com" is "xn--maana-pta.com".

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux

<?php

include("chilkat.php");
// Use "chilkat_9_5_0.php" for versions of Chilkat < 10.0.0


$sb = new CkStringBuilder();

// Load the string "café" from a utf-8 text file.
$success = $sb->LoadFile('qa_data/txt/cafe.txt','utf-8');

$sb->PunyEncode();
print $sb->getAsString() . "\n";

$sb->PunyDecode();
print $sb->getAsString() . "\n";

// The output is:
// 
// caf-dma
// café

?>