session_start(): Cannot send session cookie

[learntophp]

PHP 4.3.6

Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /web/htdocs/htdocs/index.php:1) in auth.php on line 2

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /web/htdocs/htdocs/index.php:1) in auth.php on line 2
You are not authenticated. Please login.


Are the errors I am gettting usin ght efollowing code:

<?
session_start();
include ("connect.php");

// convert username and password from _POST or _SESSION
if($_POST["username"])
{
$username=$_POST["username"];
$password=$_POST["password"];
}
elseif($_SESSION["username"])
{
$username=$_SESSION["username"];
$password=$_SESSION["password"];
}

// start and register session variables
session_register("username");
session_register("password");

// query for a user/pass match
$result=mysql_query("select * from users
where username='" . $username . "' and password='" . $password . "'");

// retrieve number of rows resulted
$num=mysql_num_rows($result);

// print login form and exit if failed.
if($num < 1){
session_destroy();
echo "You are not authenticated. Please login.<br><br>
<form method=POST action=index.php>
username: <input type=text name=\"username\">
password: <input type=password name=\"password\">
<input type=submit>
</form>";

exit;
}
?>
-------------------------------link_1.php

<?
include("auth.php");

// begin content
include("nav.php");

echo "This is my home page.";
?>

Any ideas on how the fix this?

[joe_bruin]

remove the empty lines and white-space before the "<?" at the beginning of your files.

[sammy]

If you read the error message, it says that index.php has already sent the headers to the client. Im guessing your doing an include in index.php to include this file you are using. If you are, then you need to remove any print statements before the include statement in index.php .
This is why I dont have too many linked includes. Gets messy