print_r($_SERVER); 해서 찾으삼

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'];
}

$_SERVER['REMOTE_ADDR'] ..

내장함수 찾아보셔용~