PHP记录访问ip代码

<?php
 public function ipaddress() {
                global $ip;
                if(getenv("HTTP_CLIENT_IP"))
                        $ip=getenv("HTTP_CLIENT_IP");
                else if(getenv("HTTP_X_FORWARDED_FOR"))
                        $ip=getenv("HTTP_X_FORWARDED_FOR");
                else if(getenv("REMOTE_ADDR"))
                        $ip=getenv("REMOTE_ADDR");
                else
                        $ip="Unknow";
               return $ip;
 }
echo ipaddress();
?>