title: regex validation cyrillic domain
body: <p>I need to write a regular expression to validate Latin and Cyrillic domain name.
  I wrote this function, but it does not work with Cyrillic domains. 
  Tell me what's wrong?</p>
  
  <pre><code>function isDomain($url)
      {
          if (mb_strlen($url)==0) return false;
          $url = mb_strtolower(trim($url));
          $abc = 'абвгдеёжзийклмнопрстуфхцчшщэьъыюя';
          if(!preg_match('/^(['.$abc.'a-z0-9\.-]{1,64})?\.(?:рф|ru|su|com|net|org|mil|edu|arpa|gov|biz|info|aero|inc|name|[a-z]{3})$/i',$url))
          {
              return FALSE; 
          } else {
              return TRUE;
          }
      }
  </code></pre>