php学习 获得客户端IP函数

function getip()
{
if(getenv('HTTP_CLIENT_IP'))
{
  $client_ip = getenv('HTTP_CLIENT_IP');
}
elseif(getenv('HTTP_X_FORWARDED_FOR'))
{
  $client_ip = getenv('HTTP_X_FORWARDED_FOR');
}
elseif(getenv('REMOTE_ADDR'))
{
  $client_ip = getenv('REMOTE_ADDR');
}
else
{
  $client_ip = $HTTP_SERVER_VAR['REMOTE_ADDR'];
}
  return $client_ip;
}