The hello and goodbye friend is still appearing in the navigation items when i have used 'type' => MENU_CALLBACK,

<?php

function greeting_menu() {
    $items = array();
    $items['hello_friend'] = array(
            'title' => "Hello Friend!",
            'page callback' => 'say_hello',
            'access callback' => TRUE,
            'type' => MENU_CALLBACK,
    );
    $items['goodbye'] = array(
        'title' => 'Goodbye Friend!',
        'page callback' => 'say_goodbye',
        'access callback' => TRUE,
        'type' => MENU_CALLBACK,
    );
    return $items;
}

function say_hello() {
    return '<p>Hello my dear friend!</p>';
}

function say_goodbye() {
    return '<p> Goodbye my dear friend </p>';
}

function greeting_user_login() {
    $_GET['destination'] = 'hello_friend';
}

function greeting_user_logout() {
    $_GET['destination'] = 'goodbye';

}