error trying to log in

[craig_thompson]

this is the error message i get when i try to login to my data base

Warning: session_register() [function.session-register]: Cannot send session cache limiter - headers already sent (output started at D:\virtualservers\182763\root\test\login\checklogin.php:1) in D:\virtualservers\182763\root\test\login\checklogin.php on line 26

Warning: Cannot modify header information - headers already sent by (output started at D:\virtualservers\182763\root\test\login\checklogin.php:1) in D:\virtualservers\182763\root\test\login\checklogin.php on line 28

here is the script i have that i am logiing in with

<?php

$host=""; // Host name
$username=""; // Mysql username
$password=""; // Mysql password
$db_name=""; // Database name
$tbl_name=""; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");

// Define $myusername and $mypassword
$myusername=$POST['myusername'];
$mypassword=$POST['mypassword'];

$sql="SELECT * FROM $tbl_name WHERE username='$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 "login_success.php"
session_register("myusername");
session_register("mypassword");
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}

ob_end_flush();
?>

can anybody please point out where i have gone wrong

thanks

[jkurrle]

Try putting an "exit;" command after the header and see if it helps...

[craig_thompson]

so which part is the header?

i am sorry i am very new to this
do you mean the header on the page ?
or is it after a particular line

thanks

[jkurrle]

header("location:login_success.php");
exit;

[bradgrafelman]

1. An exit after the header, while generally seen as good practice, is not your problem. PHP told you what the problem is:

   output started at D:\virtualservers\182763\root\test\login\checklogin.php:1

   There's data that's being sent before the <?php tag at the beginning, be it a blank space, Unicode BOM, something.

2. Also note that your script is vulnerable to SQL injection attacks. User-supplied data should never be placed directly into a SQL query; instead it should first be sanitized with a function such as [man]mysql_real_escape_string/man.

3. [man]session_register/man has been deprecated for some time. Instead, you should call [man]session_start/man at the top of the script and insert data into the session via the $_SESSION superglobal array.