PHP获取用户的真实IP地址，非代理IP

function getClientIP(){      global $ip;      if(getenv("HTTP_CLIENT_IP")){        $ip = getenv("HTTP_CLIENT_IP");      }else if(getenv("HTTP_X_FORWARDED_FOR")){        $ip = getenv("HTTP_X_FORWARDED_FOR");      }else if(getenv("REMOTE_ADDR")){        $ip = getenv("REMOTE_ADDR");      }else{        $ip = "NULL";      }    return $ip;  }