Warning: mysql_num_rows()

Hi folks,

I'm new to this forum, and to the world of MySQL. I'll openly admit that I'm completely out of my depth on this one, but maybe one of you will be kind enough to provide some input that may help me.

I have created a database according to the 'foolproof' instructions given with a free resource from http://www.stevedawson.com/propertyplus.php This (PHP PropertyPlus) is for the management of property details. Everything seemed to go according to plan, but there is an error when logging in as follows:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/bulgaria/public_html/admin/index.php on line 32

The relevant section is here:
__________________________________________________ ____________
$validationattempted = false;
include "config.php";
if (isset($_POST["op"]) && ($_POST["op"]=="adminlogin"))
{
mysql_connect($server, $DBusername, $DBpassword) or die ("$DatabaseError");
mysql_select_db($database);
$query = "SELECT * FROM $admin_table WHERE admin_username='".$_POST['admin_username']."' AND admin_password='".$_POST['admin_password']."'";
$result = mysql_query($query);
if (mysql_num_rows($result) >0 )
{
$validationattempted = true;
$validated = true; // assume validation passed
// If username and password are vaild set the cookie
setcookie ("ValidUserAdmin", $_POST['admin_username'],time()+36000); // expire in 1 hour
__________________________________________________ ____________

Oh dear, might just as well be written in Klingon... Can anyone see anything obviously wrong? Line 32 is the 'mysql_num_rows' bit...

Don't know if I've provided enough info here, let me know if you need more and I will attempt to provide it!

Hope to hear from some kind soul, regards,

Vince

There's a good chance your query failed... add or die() to the end of your mysql_query line