Need some help with gethostbyaddr

Getting this warning

Warning: gethostbyaddr() [function.gethostbyaddr]: Address is not a valid IPv4 or IPv6 address in /home/mobsters/public_html/signup.php on line 312

Code (markup):

Line 312 is

$host=gethostbyaddr("$REMOTE_ADDR");

Code (markup):

Anyone know what it could be?

 

$_SERVER['REMOTE_ADDR']

Re's
Rob Whisonant

 

Just to clarify Rob's response:

echo getHostByAddr($_SERVER['REMOTE_ADDR']);

 

But check out the REMOTE_ADDR some sites/proxy will give another not valid ip address!