To prevent ip spoofing

If the following code prevents ip spoofing, it is used to obtain the client IP address: if (getenv ('http _ CLIENT_IP ') & amp; strcasecmp (getenv ('http _ CLIENT_IP '), 'unknon') {& nbsp; $ onlineip = getenv ('http _ CLIE if the ip address is not forged
Run the following code to obtain the client IP address:
If (getenv ('http _ CLIENT_IP ') & strcasecmp (getenv ('http _ CLIENT_IP'), 'Unknown ')){
$ Onlineip = getenv ('http _ CLIENT_IP ');
} Elseif (getenv ('http _ X_FORWARDED_FOR ') & strcasecmp (getenv ('http _ X_FORWARDED_FOR'), 'Unknown ')){
$ Onlineip = getenv ('http _ X_FORWARDED_FOR ');
} Elseif (getenv ('remote _ ADDR ') & strcasecmp (getenv ('remote _ ADDR'), 'Unknown ')){
$ Onlineip = getenv ('remote _ ADDR ');
} Elseif (isset ($ _ SERVER ['remote _ ADDR ']) & $ _ SERVER ['remote _ ADDR '] & strcasecmp ($ _ SERVER ['remote _ ADDR'], 'Unknown ')){
$ Onlineip = $ _ SERVER ['remote _ ADDR '];
}
However, all request headers starting with HTTP _ belong to messages that can be forged on the client. in the reverse proxy environment, how can I ensure that PHP will not receive forged invalid HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR values?


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What is the relationship between reverse proxy and forged IP addresses?

IP address cannot be fraudulent. if you want to cheat, you must use a proxy server to request you. what can you do?
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Although the IP address on the proxy or vpn is not his own, it is a genuine IP address, just like shopping, let your store buy something called Xiao Wang, he is really called Xiao Wang, when Mr. Smith leaves, I tell him that Mr. Smith is buying something for others.