PHP 获取客户端 IP 地址

先来了解一个变量的含义：

$_server['remote_addr']：浏览当前页面的用户计算机的ip地址

$_server['http_client_ip']：客户端的ip

$_server['http_x_forwarded_for']：浏览当前页面的用户计算机的网关

$_server['http_x_real_ip']：nginx 代理模式下，获取客户端真实ip

/**
 *  获取客户端ip地址
 */
function real_ip()
{
    $ip = $_server['remote_addr'];
    if (isset($_server['http_x_forwarded_for']) && preg_match_all('#\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}#s', $_server['http_x_forwarded_for'], $matches)) {
        foreach ($matches[0] as $xip) {
            if (!preg_match('#^(10|172\.16|192\.168)\.#', $xip)) {
                $ip = $xip;
                break;
            }
        }
    } elseif (isset($_server['http_client_ip']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', $_server['http_client_ip'])) {
        $ip = $_server['http_client_ip'];
    } elseif (isset($_server['http_cf_connecting_ip']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', $_server['http_cf_connecting_ip'])) {
        $ip = $_server['http_cf_connecting_ip'];
    } elseif (isset($_server['http_x_real_ip']) && preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', $_server['http_x_real_ip'])) {
        $ip = $_server['http_x_real_ip'];
    }
    return $ip;
}