How does PHP get the IP location?

How does PHP get the IP location?
I call the interface of QQ

    
    
    
    
    
    
    
    
    Preg_match ("@(. *)

    
    

The output indicates that my IP can only be used inside the LAN, I am in the school, there is no API to get the address AH




Baidu a bit IP will be able to find out the address, this is how to do


------to solve the idea----------------------
I know Baidu has an API to get city http://api.map.baidu.com/location/ip?ak=xxx according to IP
To apply for AK
------to solve the idea----------------------
$url = ' http://ip.taobao.com/service/getIpInfo.php?ip= '. $Ip;
#json格式的数据
Does not pass IP, is your current public network IP data.
You pass in the intranet IP (such as 192.168***, etc.), it is certainly not recognized the HA
------to solve the idea----------------------
You can only get the IP of the extranet.

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