Detect Clients with Proxy Servers via PHP

Detect clients with Proxy Servers via PHP

You can't detect that unless they pass on special headers which explictly mention it like X-Forwarded-For or something.

As far as I know you have to use a blacklist. Users who use putty portforwarding, VPN or other more sophisticated methods are undetactable as they behave exactly like normal users.

Detecting whether a user is behind a proxy

TOR does not supply any server headers such as X_FORWARDED_FOR, so your best bet is to use a list of all known exit nodes. A list can be found at https://torstat.xenobite.eu/.

For other proxies, you can look at server headers. Possible server headers of interest include:

HTTP_VIA 
HTTP_X_FORWARDED_FOR
HTTP_FORWARDED_FOR 
HTTP_X_FORWARDED
HTTP_FORWARDED 
HTTP_CLIENT_IP
HTTP_FORWARDED_FOR_IP 
VIA
X_FORWARDED_FOR 
FORWARDED_FOR
X_FORWARDED FORWARDED
CLIENT_IP
FORWARDED_FOR_IP
HTTP_PROXY_CONNECTION

In PHP, you can get the value of these fields in the $_SERVER[] superglobal.

Finding IP address of client connected through a proxy

The standard solution (in php) is:

if ($_SERVER['HTTP_X_FORWARDED_FOR']){
    $ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
} 
else{ 
    $ip = $_SERVER['REMOTE_ADDR'];
}

But as the first answer says this all depends on the header actually being set.

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