doLogin.php #1 [Mike M. tutorial]

<?php
require("functions.class.php");
$functions = new functions;

@$username = strip_tags($_POST['username']);
@$password = strip_tags($_POST['password']);

/*WARNING LIST
1:wrong username + password combination
2:username is not found
3:username and/or password might be empty
4:username is not alphanumeric OR haven't got the correct length
5:password haven't got the correct length / or invalid characters
*/

//echo($functions->username_exists("admin"));
//echo($functions->receive_password("admin"));
//echo($functions->receive_salt("admin"));
//echo($functions->equal_password("admin","password"));

if(!empty($username) && !empty($password)){
    //username and password is filled in.
    if($functions->check_username($username) == true){
        //username exists
        if($functions->username_exists($username) == true){
            //username is alphanumeric and has the correct length(s)
            if($functions->check_password($password) == true){
                //password has the correct length
                if($functions->equal_password($username, $password) == true){
                    //username and password is correct
                    echo("Successfully Logged In");
                }else{
                    //username and/or password combination is incorrect!
                    header("Location: login.php?id=1");
                    echo("Reloading...");
                }
            }else{
                //password haven't got the correct length or contains disallowed characters
                header("Location: login.php?id=5");
                echo("Reloading...");
            }
        }else{
            //username does not exist
            header("Location: login.php?id=2");
            echo("Reloading...");
        }
    }else{
        //username is not alphanumeric and/or haven't got the correct length(s)
        header("Location: login.php?id=4");
        echo("Reloading...");
    }
}else{
    //username and/or password is not filled in.
    header("Location: login.php?id=3");
    echo("Reloading...");
}
?>