function login(){
        global $db, $username, $errors;

        // grap form values
        $username = e($_POST['username']);
        //$email = e($_POST['email']);
        $password = e($_POST['password']);

        // make sure form is filled properly
        if (empty($username)) {
            array_push($errors, "Usuario es Requerido");
        }
        if (empty($password)) {
            array_push($errors, "Contraseña es Requerida");
        }

        // attempt login if no errors on form
        if (count($errors) == 0) {
            $password = md5($password);

            $query = ("SELECT * FROM users WHERE username='$username' AND password='$password' LIMIT 1");
            $results = mysqli_query($db, $query);

            if (mysqli_num_rows($results) == 1) { // user found
                // check if user is admin or user
                $logged_in_user = mysqli_fetch_assoc($results);
                if ($logged_in_user['user_type'] == 'admin') {

                    $_SESSION['user'] = $logged_in_user;
                    $_SESSION['success']  = "Usted se ha conectado";
                    header('location: admin/home.php');
                }else{
                    $_SESSION['user'] = $logged_in_user;
                    $_SESSION['success']  = "Usted se ha conectado";

                    header('location: index.php');
                }
            }else {
                array_push($errors, "Combinación incorrecta de nombre de usuario/contraseña");
            }
        }
    }