here is how i changed the code..
<?php
$ip=$_SERVER['REMOTE_ADDR'];
echo"you ip adddress is".$ip;
$isp=gethostbyaddr($ip);
echo $isp;
?>
and the output i got is
you ip adddress is **.**.177.233 **.**.177.233
that means it is returning me the ip address again, instead if ISP name ..