class WPDesk_Post_Not_Exists_Exception extends \Exception {
}

/**
 * @return \WP_Post
 * @throws \WPDesk_Post_Not_Exists_Exception
 */
function get_wpdesk_post() {
    $post = get_post(123);
    if ($post) {
        return $post;
    }

    throw new WPDesk_Post_Not_Exists_Exception('WPDesk post 123 is not available in the database');
}

/**
 * @return string
 * @throws \WPDesk_Post_Not_Exists_Exception
 */
function get_wpdesk_post_title() {
    return get_wpdesk_post()->post_title;
}

/**
 * @throws \WPDesk_Post_Not_Exists_Exception 
 */
function display_wpdesk_title() {
    echo get_wpdesk_post_title();
}

try {
    display_wpdesk_title();
} catch (\WPDesk_Post_Not_Exists_Exception $not_exists) {
    echo 'Some placeholder title';
}