我很惊讶没有人提到filter_input，所以这里是Alix Axel的回答浓缩成一行:

function get_ip_address(&$keys = ['HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'HTTP_CLIENT_IP', 'REMOTE_ADDR'])
{
    return empty($keys) || ($ip = filter_input(INPUT_SERVER, array_pop($keys), FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE))? $ip : get_ip_address($keys);
}

我们使用:

/**
 * Get the customer's IP address.
 *
 * @return string
 */
public function getIpAddress() {
    if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
        return $_SERVER['HTTP_CLIENT_IP'];
    } else if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $ips = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
        return trim($ips[count($ips) - 1]);
    } else {
        return $_SERVER['REMOTE_ADDR'];
    }
}

在HTTP_X_FORWARDED_FOR上的爆炸是因为我们在使用Squid时检测IP地址的奇怪问题。

/**
 * Sanitizes IPv4 address according to Ilia Alshanetsky's book
 * "php|architect?s Guide to PHP Security", chapter 2, page 67.
 *
 * @param string $ip An IPv4 address
 */
public static function sanitizeIpAddress($ip = '')
{
if ($ip == '')
    {
    $rtnStr = '0.0.0.0';
    }
else
    {
    $rtnStr = long2ip(ip2long($ip));
    }

return $rtnStr;
}

//---------------------------------------------------

/**
 * Returns the sanitized HTTP_X_FORWARDED_FOR server variable.
 *
 */
public static function getXForwardedFor()
{
if (isset($_SERVER['HTTP_X_FORWARDED_FOR']))
    {
    $rtnStr = $_SERVER['HTTP_X_FORWARDED_FOR'];
    }
elseif (isset($HTTP_SERVER_VARS['HTTP_X_FORWARDED_FOR']))
    {
    $rtnStr = $HTTP_SERVER_VARS['HTTP_X_FORWARDED_FOR'];
    }
elseif (getenv('HTTP_X_FORWARDED_FOR'))
    {
    $rtnStr = getenv('HTTP_X_FORWARDED_FOR');
    }
else
    {
    $rtnStr = '';
    }

// Sanitize IPv4 address (Ilia Alshanetsky):
if ($rtnStr != '')
    {
    $rtnStr = explode(', ', $rtnStr);
    $rtnStr = self::sanitizeIpAddress($rtnStr[0]);
    }

return $rtnStr;
}

//---------------------------------------------------

/**
 * Returns the sanitized REMOTE_ADDR server variable.
 *
 */
public static function getRemoteAddr()
{
if (isset($_SERVER['REMOTE_ADDR']))
    {
    $rtnStr = $_SERVER['REMOTE_ADDR'];
    }
elseif (isset($HTTP_SERVER_VARS['REMOTE_ADDR']))
    {
    $rtnStr = $HTTP_SERVER_VARS['REMOTE_ADDR'];
    }
elseif (getenv('REMOTE_ADDR'))
    {
    $rtnStr = getenv('REMOTE_ADDR');
    }
else
    {
    $rtnStr = '';
    }

// Sanitize IPv4 address (Ilia Alshanetsky):
if ($rtnStr != '')
    {
    $rtnStr = explode(', ', $rtnStr);
    $rtnStr = self::sanitizeIpAddress($rtnStr[0]);
    }

return $rtnStr;
}

//---------------------------------------------------

/**
 * Returns the sanitized remote user and proxy IP addresses.
 *
 */
public static function getIpAndProxy()
{
$xForwarded = self::getXForwardedFor();
$remoteAddr = self::getRemoteAddr();

if ($xForwarded != '')
    {
    $ip    = $xForwarded;
    $proxy = $remoteAddr;
    }
else
    {
    $ip    = $remoteAddr;
    $proxy = '';
    }

return array($ip, $proxy);
}

就像之前有人说的，这里的关键在于你为什么想要存储用户的ip。

我将从我工作的注册系统中给出一个例子，当然解决方案只是为了在这个经常出现在我搜索中的旧讨论中贡献一些东西。

许多php注册库使用ip来限制/锁定基于用户ip的失败尝试。 看看这张表:

-- mysql
DROP TABLE IF EXISTS `attempts`;
CREATE TABLE `attempts` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `ip` varchar(39) NOT NULL, /*<<=====*/
  `expiredate` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 -- sqlite
...

然后，当用户尝试登录或任何与重置密码相关的服务时，在开始时调用一个函数:

public function isBlocked() {
      /*
       * used one of the above methods to capture user's ip!!!
       */
      $ip = $this->ip;
      // delete attempts from this ip with 'expiredate' in the past
      $this->deleteAttempts($ip, false);
      $query = $this->dbh->prepare("SELECT count(*) FROM {$this->token->get('table_attempts')} WHERE ip = ?");
      $query->execute(array($ip));
      $attempts = $query->fetchColumn();
      if ($attempts < intval($this->token->get('attempts_before_verify'))) {
         return "allow";
      }
      if ($attempts < intval($this->token->get('attempts_before_ban'))) {
         return "captcha";
      }
      return "block";
   }

例如，$this->令牌->get('attempts_before_ban') === 10和2个用户来相同的ips，就像前面的代码中头部可以被欺骗的情况一样，然后在5次尝试后，两者都被禁止! 更糟糕的是，如果所有用户都来自同一个代理，那么只有前10个用户将被记录，其余的用户将被禁止!

这里的关键是我们需要一个表尝试的唯一索引，我们可以从这样的组合中获得它:

 `ip` varchar(39) NOT NULL,
 `jwt_load varchar(100) NOT NULL

其中jwt_load来自一个遵循json web令牌技术的HTTP cookie，我们只存储加密的有效负载，应该包含每个用户的任意/唯一值。 当然，请求应该修改为:"SELECT count(*) FROM {$this->token->get('table_attempts')} WHERE ip = ?AND jwt_load = ?"并且该类还应该初始化一个私有的$jwt。

我很惊讶没有人提到filter_input，所以这里是Alix Axel的回答浓缩成一行:

function get_ip_address(&$keys = ['HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'HTTP_CLIENT_IP', 'REMOTE_ADDR'])
{
    return empty($keys) || ($ip = filter_input(INPUT_SERVER, array_pop($keys), FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE))? $ip : get_ip_address($keys);
}

i realize there are much better and more concise answers above, and this isnt a function nor the most graceful script around. In our case we needed to output both the spoofable x_forwarded_for and the more reliable remote_addr in a simplistic switch per-say. It needed to allow blanks for injecting into other functions if-none or if-singular (rather than just returning the preformatted function). It needed an "on or off" var with a per-switch customized label(s) for platform settings. It also needed a way for $ip to be dynamic depending on request so that it would take form of forwarded_for.

我也没有看到任何人地址isset() vs !empty()——它可能没有为x_forwarded_for输入任何内容，但仍然触发isset()真理导致空白var，一种解决方法是使用&&并结合两者作为条件。请记住，您可以欺骗像“PWNED”这样的单词为x_forwarded_for，因此，如果您的输出在某个受保护的地方或到DB中，请确保您将其杀菌为真实ip语法。

此外，如果您需要一个多代理来查看x_forwarder_for中的数组，则可以使用谷歌translate进行测试。如果你想欺骗头部测试，检查这个Chrome客户端头部欺骗扩展。这将默认只是标准的remote_addr，而后面的一个代理。

我不知道任何情况下，remote_addr可以是空的，但它在那里，以防万一。

// proxybuster - attempts to un-hide originating IP if [reverse]proxy provides methods to do so
  $enableProxyBust = true;

if (($enableProxyBust == true) && (isset($_SERVER['REMOTE_ADDR'])) && (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) && (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))) {
    $ip = end(array_values(array_filter(explode(',',$_SERVER['HTTP_X_FORWARDED_FOR']))));
    $ipProxy = $_SERVER['REMOTE_ADDR'];
    $ipProxy_label = ' behind proxy ';
} elseif (($enableProxyBust == true) && (isset($_SERVER['REMOTE_ADDR']))) {
    $ip = $_SERVER['REMOTE_ADDR'];
    $ipProxy = '';
    $ipProxy_label = ' no proxy ';
} elseif (($enableProxyBust == false) && (isset($_SERVER['REMOTE_ADDR']))) {
    $ip = $_SERVER['REMOTE_ADDR'];
    $ipProxy = '';
    $ipProxy_label = '';
} else {
    $ip = '';
    $ipProxy = '';
    $ipProxy_label = '';
}

为了使这些动态用于下面的函数或查询/回显/视图，比如日志生成或错误报告，使用全局变量或在任何你想要的地方回显em，而不需要创建大量其他条件或静态模式输出函数。

function fooNow() {
    global $ip, $ipProxy, $ipProxy_label;
    // begin this actions such as log, error, query, or report
}

谢谢你的好想法。请让我知道如果这可以更好，仍然有点新的这些头:)