login page does not execute a else statement

Posted on 16th Feb 2014 by admin

I've created a login page using sessions.
When an incorrect user name or password is entered then a custom messege error message apears.

But if a correct user name and password is used then notthing happens, no error message and I'm still on the login form.

This is the code below.
What am I'm doing wrong?

Code:
<?php
include("config.php");

$id = strip_tags($_GET['id']);

if ($id == "do") {
$user = strip_tags($_POST['username']);
$pass = strip_tags($_POST['password']);

if ($user == $username and $pass == $password) {

session_start();
session_register('authorized');
$_SESSION['authorized'] = true;

header("Location: admin.php");
exit;

} else {
echo "<p>Incorect Username or/and Password, Please Go back and try again.</p>";
}
} else {

?>
<form method="POST" action="login.php?id=do">
<input type="text" name="username">
<input type="password" name="password">
<input type="submit" value="Login">
</form>
<?php
}
?>

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