session/header problems

[troinfo]

I'm trying validate a user and then send him/her to another page if they are valid. Plus check that the $login is there by calling the session on that page to make sure that the person did login.

The validation works fine but I get this error:

Warning: Cannot add header information - headers already sent by (output started at /*//.php:3) in //*//***.php on line 39

plus I have some java script on the page and the SID gets written to it and causes an error too.

this is line 1 ---> <?session_start();?>

<?

if($action)

{

if ((!$username) || (!$password))
{

$msg = "Must enter Username or Password";

} 

$db_name = "*****";

$table_name = "*******";

$connection = mysql_connect("***", "*", "*******") or die("Couldn't connect.");

$db = mysql_select_db($db_name, $connection) or die("Couldn't select database.");

$sql = "select username and password from $table_name where username ='$username' and password ='$password'";

$result = mysql_query($sql,$connection) or die("Couldn't execute query 1.");

$num = mysql_num_rows($result);

if ($num == 0)

 {

$msg = "Bad Login try again.";

 }

if ($num !=0)

 {

$login = $username;
session_register("login");
header("location: /*/***.php");
exit;

 }

}
?>

Any help would be great. Thanks

[flipis]

If you echo, print or show ANY text on the page BEFORE calling header, header will not work. You can't echo anything before.

Try this code in a small script (call it trying.php)

<?
header("Location:http://www.phpbuilder.com");
?>

Now try this one (call it trying2.php)

<?
echo "fLIPIS is my friend";
header("Location:http://www.phpbuilder.com");
?>

See?

Proably your $num variable is 0 and that's why it echoes "Bad login, try again"

Hope it helps

fLIPIS