用php来检测proxy

能够检测大部分通过代理服务器访问的ip. 
//beiji.com 2000.6.17
$ip = getenv("REMOTE_ADDR");
$v = getenv("HTTP_VIA");
$f = getenv("HTTP_X_FORWARDED_FOR");
$c = getenv("HTTP_XROXY_CONNECTION");
$o = getenv("HTTP_PRAGMA");

print '
REMOTE_ADDR';  
print $ip;  

if (($v=="")&&($f=="")&&($c=="")&&($o=="")){  
print "
not through proxy";  
}  
else {  
print "
through proxy";  
print '
http_via: ';print $v;  
print '
http_x_forwarded_for: ';print $f;  
print '
http_xroxy_connection: ';print $c;  
print '
http_pragma: ';print $o;  
}  
?>