PHP 函数 ip2long

<?php
   $ip = gethostbyname('www.codingdict.com');
   $out = "The following URLs are equivalent:
   \n";

   $out .= 'http://www.codingdict.com/, http://' . $ip . '/,
      and http://' . sprintf("%u", ip2long($ip)) . "/
   \n";

   echo $out;
?>