[objx]

Glömde du redovisa var du deklarerar $numrows?
Enklaste lösningen utifrån din kod borde vara detta:

$query = mysql_query(sprintf("SELECT * FROM admuser WHERE username='%s' AND password='%s'",
mysql_real_escape_string($username),
mysql_real_escape_string($password)));


if($query && mysql_num_rows($query) > 0)
{
while ($row = mysql_fetch_assoc($query))
osv.