用php来检测proxy

能够检测大部分通过代理服务器访问的ip.
<?php 
//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 '<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; 
} 
?>