PHP: Showing the Remote Address

<source_code>
<form name="thisform" method="POST" action="http://ws.arin.net/cgi-bin/whois.pl">
<input type="text" Name="queryinput" size="15" maxsize="15" value="<?php echo ${REMOTE_ADDR}; ?>">
<input type="submit" value="<--this is your external IP">
</form>
</source_code>