Proteggere directory o pagine con password [Non è la solita domanda...]

[nico95]

session_start();  

include 'db.php';
$username = $_POST['username'];
$password = $_POST['password'];

if((!$username) || (!$password)){
    echo "Please enter ALL of the information! 
";
    include 'index.htm';
    exit();
}

$password = md5($password);

$sql = mysql_query("SELECT * FROM users WHERE username='$username' AND password='$password' AND activated='1'");
$login_check = mysql_num_rows($sql);

if($login_check > 0){
    while($row = mysql_fetch_array($sql)){
    foreach( $row AS $key => $val ){
        $$key = stripslashes( $val );
    }
        session_register('first_name');
        $_SESSION['first_name'] = $first_name;
        session_register('last_name');
        $_SESSION['last_name'] = $last_name;
        session_register('email_address');
        $_SESSION['email_address'] = $email_address;
        
        header("Location: sample.php");
    }
} else {
    echo "You could not be logged in! Either the username and password do not match or you have not validated your membership!

    Please try again!
";
    include 'index.html';
}
?> 

Io attualmente utilizzo questo script... (ovviamente è soltanto la parte che riguarda i controlli), io non sono tanto bravo col php non è che potresti darmi qualche diritta...