警告：mysql_num_rows（）希望参数1是资源，布尔值在第15行的C:\xampp\htdocs\app\tpl\skins\Habbo\register.php中给出

当我尝试在我的游戏中注册帐户时，会出现以下错误：

Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\app\tpl\skins\Habbo\register.php on line 15

代码如下：

<?php

$iphone = strpos($_SERVER['HTTP_USER_AGENT'],"iPhone");
$android = strpos($_SERVER['HTTP_USER_AGENT'],"Android");
$palmpre = strpos($_SERVER['HTTP_USER_AGENT'],"webOS");
$berry = strpos($_SERVER['HTTP_USER_AGENT'],"BlackBerry");
$ipod = strpos($_SERVER['HTTP_USER_AGENT'],"iPod");

if ($iphone || $android || $palmpre || $ipod || $berry == true) 
{ 
  echo "You cant register on a mobile device!";
  die();
}
$checkAccounts = mysql_query("SELECT * FROM users WHERE ipaddress_reg = '".$_SERVER['REMOTE_ADDR']."'");
if(mysql_num_rows($checkAccounts) > 1)
{
  echo 'You can only create 2 accounts at the most, sorry.';
  die();
}
?>

试试这个：

if($checkAccounts!=FALSE && mysql_num_rows($checkAccounts) > 1)

而且mysql函数已被弃用，最好使用mysqli。查看PHP参考了解更多信息。
您无法在移动设备上注册WTF？！顺便说一下，您似乎忘记打开数据库连接。