show-admin-toolbar.php

//Disallow direct access
defined( 'ABSPATH' ) or die( 'No Access' );

function wpb_bring_admin_back() {
    if ( is_user_logged_in() && current_user_can('manage_options') ) {
        add_filter( 'show_admin_bar' , '__return_true' );
        show_admin_bar( true );
    }
}

add_action( 'wp_loaded', 'wpb_bring_admin_back', 10000 );