WordPress - Remove menu or sub-menu page

functions.php

/* ==========================================
Put the following code at the end of wp-config.php file to remove menu or sub-menu page.
========================================== */

/* *********
Line 10 will remove menu page of plugin: BackWPup
Line 11 will remove Settings menu
********* */
function dcg_custom_menu_page_removing() {
	remove_menu_page( 'backwpup' );
	remove_menu_page( 'settings' );
	
	/* To remove a settings page for plugins that use a slug like /wp-admin/options-general.php?page=wp-performance-score-booster use this code: */
	remove_submenu_page( 'options-general.php', 'wp-performance-score-booster' );
}
add_action( 'admin_menu', 'dcg_custom_menu_page_removing' );