(PHP 5 >= 5.3.0, PECL intl >= 1.0.2, PECL idn >= 0.1)
idn_to_utf8 — Convert domain name from IDNA ASCII to Unicode.
Procedural style
$domain
   [, int $options = 0
   [, int $variant = INTL_IDNA_VARIANT_2003
   [, array &$idna_info
  ]]] )This function converts Unicode domain name from IDNA ASCII-compatible format to plain Unicode, encoded in UTF-8.
domainDomain to convert in IDNA ASCII-compatible format.
optionsConversion options - combination of IDNA_* constants (except IDNA_ERROR_* constants).
variant
       Either INTL_IDNA_VARIANT_2003 for IDNA 2003 or
       INTL_IDNA_VARIANT_UTS46 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_*.
      
   Domain name in Unicode, encoded in UTF-8.  or FALSE on failure
  
| Version | Description | 
|---|---|
| 5.4.0/PECL 2.0.0b1 | Added the parameters variantandidna_info; UTS #46 support. | 
Example #1 idn_to_utf8() example
<?php
echo idn_to_utf8('xn--tst-qla.de'); 
?>
The above example will output:
täst.de