获取客户端IP

 function getIP(){
     $ip = "";
     if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))
         $ip = getenv("HTTP_CLIENT_IP");
     else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown"))
         $ip = getenv("HTTP_X_FORWARDED_FOR");
     else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown"))
         $ip = getenv("REMOTE_ADDR");
     else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown"))
         $ip = $_SERVER['REMOTE_ADDR'];
     else
         $ip = "0.0.0.0";
     return $ip;
 }