I am getting an error with my login script:

Error:

Warning: Cannot modify header information - headers already sent by (output started at /home/bucket/public_html/inc/config.php:7) in /home/bucket/public_html/checklogin.php on line 24

checklogin.php

PHP Code:

<?php
include "inc/config.php";
// username and password sent from form
$myusername=$_POST['myusername'];
$mypassword=$_POST['mypassword'];
// To protect MySQL injection (more detail about MySQL injection)
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);
$sql="SELECT * FROM `admin` WHERE username='$myusername' and password='$mypassword'";
$result=mysql_query($sql);
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);
// If result matched $myusername and $mypassword, table row must be 1 row
if($count==1){
// Register $myusername, $mypassword and redirect to file "accounts.php"
session_register("myusername");
session_register("mypassword");
header("location:accounts.php");
}
else 
{
header( 'Location: accounts-login.php' ) ;
}
?>

Does anyone spot the problem?

You cannot set sessions or send headers AFTER output is sent to the browser

That is, make sure there are no echo or print before the header() call, and no new lines or spaces before the opening <?php tag.

and as stated in the error message, the output has happened in config.php at line 7

(output started at /home/bucket/public_html/inc/config.php:7)