PHP获取用户真实IP地址

<?php
function getRealIP() {
$ip = '';
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} elseif (!empty($_SERVER['HTTP_CLIENT_IP'])) {
$ip = $_SERVER['HTTP_CLIENT_IP'];
} elseif (!empty($_SERVER['REMOTE_ADDR'])) {
$ip = $_SERVER['REMOTE_ADDR'];
}else{
$ip = 'Unknown';
}
return $ip;
}
?>