mysql_num_rows(): error

[tested1]

I am trying to make a login script. This script is the one that authenticates a user when he hits submit after he has registered. I am receiving Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in line 21

Here is my code.

<?php
$currentuser =
mysql_query('select * from users where username = "" .
$POST['username'] . '" and password = "' .
$POST['password'] . '"');

if (mysql_num_rows($currentuser) != 0)
{
session_start();
session_register('authorized');
$_SESSION['authorized'] = true;

header("Location: forum.php");
exit;

}

?>

Thanks

[dagon]

assuming you fix the parse error first, you will find that the query failed and returned boolean false, not the resource the mysql_num_rows expected.