终于写出个有用的东西了！
能够检测大部分通过代理服务器访问的ip.
<?php
//beiji.com2000.6.17
$ip = getenv("REMOTE_ADDR");
$v = getenv("HTTP_VIA");
$f = getenv("HTTP_X_FORWARDED_FOR");
$c = getenv("HTTP_XROXY_CONNECTION");
$o = getenv("HTTP_PRAGMA");

print '<br>REMOTE_ADDR';
print $ip;

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