用PHP如何得到访问者的真实IP

function getRealIpAddr(){
if (!empty($_SERVER['HTTP_CLIENT_IP'])){//check ip from share internet
$ip=$_SERVER['HTTP_CLIENT_IP'];
} elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])){//to check ip is pass from proxy
$ip=$_SERVER['HTTP_X_FORWARDED_FOR'];
}else{
$ip=$_SERVER['REMOTE_ADDR'];
}
return $ip;
}

function getIP(){
static $realip;
if (isset($_SERVER)){
if (isset($_SERVER["HTTP_X_FORWARDED_FOR"])){
$realip = $_SERVER["HTTP_X_FORWARDED_FOR"];
} else if (isset($_SERVER["HTTP_CLIENT_IP"])) {
$realip = $_SERVER["HTTP_CLIENT_IP"];
} else {
$realip = $_SERVER["REMOTE_ADDR"];
}
} else {
if (getenv("HTTP_X_FORWARDED_FOR")){
$realip = getenv("HTTP_X_FORWARDED_FOR");
} else if (getenv("HTTP_CLIENT_IP")) {
$realip = getenv("HTTP_CLIENT_IP");
} else {
$realip = getenv("REMOTE_ADDR");
}
}
return $realip;
}