Rookie coding problem

[Anon]

Hi,
I'm trying to forward to a URL after verifying a login.

• First i'll check that the login and password is correct.

• If it is correct i want to forward the user to a new URL.
  I'we tried Header("Location: http://www.bla.bla.url.com");
  but then I got this error:
  Cannot add header information - headers already sent

My code:
$result = mysql_query("SELECT * FROM user where username='$username' and password='$password' ");
if (mysql_num_rows($result))
{
$valid_user = $username;
session_register("valid_user");
Header("Location: http://www.bla.bla.url.com");
}
else
{
Echo ("Wrong username and/or password");
}

[matto]

there must some output before header(...), perhaps a blank line outside the php braces?
eliminate it.

if this happens, php automatically sends a html header that prevents the header() header to be sent.