php获取用户IPv4或IPv6地址的代码

<?php 
    function getIP() /*获取客户端IP*/ 
    { 
    if (@$_SERVER["HTTP_X_FORWARDED_FOR"]) 
    $ip = $_SERVER["HTTP_X_FORWARDED_FOR"]; 
    else if (@$_SERVER["HTTP_CLIENT_IP"]) 
    $ip = $_SERVER["HTTP_CLIENT_IP"]; 
    else if (@$_SERVER["REMOTE_ADDR"]) 
    $ip = $_SERVER["REMOTE_ADDR"]; 
    else if (@getenv("HTTP_X_FORWARDED_FOR")) 
    $ip = getenv("HTTP_X_FORWARDED_FOR"); 
    else if (@getenv("HTTP_CLIENT_IP")) 
    $ip = getenv("HTTP_CLIENT_IP"); 
    else if (@getenv("REMOTE_ADDR")) 
    $ip = getenv("REMOTE_ADDR"); 
    else 
    $ip = "Unknown"; 
    return $ip; 
} 
?>