php获取ip的惯用方法都是什么意思
php获取ip的常用方法都是什么意思？
问题一：
获取ip的常用方法是用$_SERVER数组的“HTTP_CLIENT_IP”、“HTTP_X_FORWARDED_FOR”、“REMOTE_ADDR”这三个元素来获取。
那这三个元素值都分别代表什么呢？
我在网上查的是:
HTTP_CLIENT_IP：代表客户端ip
HTTP_X_FORWARDED_FOR：通过代理上网的客户端ip
REMOTE_ADDR：连接ip
我的理解是：
（1）如果客户端是直接联网的：
HTTP_CLIENT_IP：显示客户端ip
HTTP_X_FORWARDED_FOR：没有
REMOTE_ADDR：显示客户端ip
（2）如果客户端是通过代理服务器的：
HTTP_CLIENT_IP：没有
HTTP_X_FORWARDED_FOR：显示客户端ip
REMOTE_ADDR：显示代理服务器ip
这么理解对吗？
问题二：
客户端的ip信息是通过header头发送过去的吧？那为什么用firefox查header头看不到相关的信息呢？
谢谢！
------解决方案--------------------
1，应该对吧，网上有一个经典的if语句，如果有需求可以拿来用，不过这只能识别君子，对小人无效。
2，HTTP_X_FORWARDED_FOR，这个应该有。其他两个REMOTE_ADDR和CLIENT_IP个人感觉是一样的东西，都是accept得到的IP，只不过是根据是否有HTTP_XFORWARDED_FOR做不同的解释而已。
------解决方案--------------------
只有 REMOTE_ADDR 反映的是用户真实的公网入口
其他的都是各种网络设备附加的内容，仅供参考
因为他们是可以随意构造的
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