php 获取用户真是IP方法

/**
 * 获取客户端IP地址
 * @param int $type 返回类型 0 返回IP地址 1 返回IPV4地址数字
 * @param bool $adv 是否进行高级模式获取（有可能被伪装）
 * @return mixed
 */
function getIP($type = 0, $adv = false)
{
    $type = $type ? 1 : 0;
    static $ip = NULL;
    if ($ip !== NULL) return $ip[$type];
    if ($adv) {
        if (isset($_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 = $_SERVER['REMOTE_ADDR'];
        }
    } elseif (isset($_SERVER['REMOTE_ADDR'])) {
        $ip = $_SERVER['REMOTE_ADDR'];
    }
    // IP地址合法验证
    $long = sprintf("%u", ip2long($ip));
    $ip   = $long ? array($ip, $long) : array('0.0.0.0', 0);
    return $ip[$type];
}

一般获取REMOTE_ADDR是不可被模拟的：$_SERVER['REMOTE_ADDR']