PHP获取客户端IP

// 获取客户端IP地址
function get_client_ip() {
static $ip = NULL;
if ($ip !== NULL) return $ip;
if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
$arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
$pos = array_search('unknown',$arr);
if(false !== $pos) unset($arr[$pos]);
$ip = trim($arr[0]);
}elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {
$ip = $_SERVER['HTTP_CLIENT_IP'];
}elseif (isset($_SERVER['REMOTE_ADDR'])) {
$ip = $_SERVER['REMOTE_ADDR'];
}
// IP地址合法验证
$ip = (false !== ip2long($ip)) ? $ip : '0.0.0.0';
return $ip;
}

摘自 lpdx111的专栏