写个自动获取访客IP的php代码

以下是一个获取访客IP的PHP代码：

$ip = '';
if (isset($_SERVER['HTTP_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_CLIENT_IP'];
} elseif (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} elseif (isset($_SERVER['HTTP_X_FORWARDED'])) {
    $ip = $_SERVER['HTTP_X_FORWARDED'];
} elseif (isset($_SERVER['HTTP_X_CLUSTER_CLIENT_IP'])) {
    $ip = $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'];
} elseif (isset($_SERVER['HTTP_FORWARDED_FOR'])) {
    $ip = $_SERVER['HTTP_FORWARDED_FOR'];
} elseif (isset($_SERVER['HTTP_FORWARDED'])) {
    $ip = $_SERVER['HTTP_FORWARDED'];
} else {
    $ip = $_SERVER['REMOTE_ADDR'];
}

解释：

该代码会检查多个HTTP请求头来获取访客的真实IP地址。它首先检查HTTP_CLIENT_IP，如果不可用，则继续检查其他请求头。如果所有请求头都没有提供IP地址，则使用REMOTE_ADDR作为最后的备选方案。请注意，这种方法并不总是可靠，因为某些代理服务器可能会隐藏或篡改请求头