Summary of various methods of obtaining the client's real IP address in PHP_PHP Tutorial

function getIP() {
if (getenv('HTTP_CLIENT_IP')) {
$ip = getenv('HTTP_CLIENT_IP');
}
elseif (getenv('HTTP_X_FORWARDED_FOR')) {
$ip = getenv(' HTTP_X_FORWARDED_FOR');
}
elseif (getenv('HTTP_X_FORWARDED')) {
$ip = getenv('HTTP_X_FORWARDED');
}
elseif (getenv('HTTP_FORWARDED_FOR')) {
$ip = getenv('HTTP_FORWARDED_FOR');

}
elseif (getenv('HTTP_FORWARDED')) {
$ip = getenv('HTTP_FORWARDED');
}
else {
$ip = $_SERVER['REMOTE_ADDR'];
}
return $ip;
}

$reIP=$_SERVER["REMOTE_ADDR"];
echo $ reIP;

if( getenv('HTTP_CLIENT_IP')) {
$onlineip = getenv('HTTP_CLIENT_IP');
} elseif(getenv('HTTP_X_FORWARDED_FOR')) {
$onlineip = getenv('HTTP_X_FORWARDED_FOR');
} elseif(getenv('REMOTE_ADDR')) {
$onlineip = getenv('REMOTE_ADDR');
} else {
$onlineip = $HTTP_SERVER_VARS['REMOTE_ADDR'];
}
echo $onlineip;

function getip_out(){
$ip=false;
if(!empty($_SERVER["HTTP_CLIENT_IP"])){
$ip = $_SERVER[" HTTP_CLIENT_IP"];
}
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$ips tutorial = explode (", ", $_SERVER['HTTP_X_FORWARDED_FOR']);
if ($ip) { array_unshift($ips, $ip); $ip = FALSE; }
for ($i = 0; $i < count($ips); $i++) {
if (!eregi ("^(10│172.16│192.168).", $ips[$i])) {
$ip = $ips[$i];
break;
}
}
}
return ($ip ? $ip : $_SERVER['REMOTE_ADDR']);
}
echo getip_out();

$user_IP = ($_SERVER["HTTP_VIA"]) ? $_SERVER["HTTP_X_FORWARDED_FOR"] : $_SERVER["REMOTE_ADDR"];
$user_IP = ($user_IP) ? $user_IP : $_SERVER["REMOTE_ADDR"];