為什麼我的每個註冊用戶的ip位址都顯示是0.0.0.0，可以確定程式碼是沒錯的

<?php

if(trim( $_POST['password'])!=trim($_POST['firmPassword'])){

   exit("兩次輸入的密碼不一致");

#}

$userName=trim($_POST['userName']);

$password=md5(trim($_POST['password']));

#$time=time ();

$ip=ip2long($_SERVER['REMOTE_ADDR']);

echo $ip;

$conn=mysqli_connect("localhost","root ","");

if(mysqli_errno($conn)){

#   echo mysqli_error($conn);

#   exit;

}

mysqli_set_charset($conn, 'utf8');

mysqli_select_db($conn,'zhuce_php');

#$sql = "insert into user(`userName`,` password`,`createtime`,`createip`) values ('" 

. $userName . "','" . $password . "','" . $ time . "','" . $ip . "')";

$result=mysqli_query($conn,$sql);

echo '目前使用者插入的ID為:' .$conn->insert_id;  

if($result){

  echo "成功<br/>";

#}else{

#  echo"失敗";

}

mysqli_close($conn);

?>