CLEAN UP OUTPUT MENU

<?php
/********* CLEAN UP OUTPUT MENU *********/
// Delete id's from menu li
add_filter( 'wp_nav_menu', 'strip_id' );
function strip_id( $menu ){
    return $menu = preg_replace('/li id=\"(.*)\"/iU', 'li', $menu );
}

// Delete all classes except "current-menu-item" - "current-menu-parent" - "custom class"
add_filter('nav_menu_css_class', 'discard_menu_classes', 10, 2);
function discard_menu_classes($classes, $item) {
    $classes = array_filter(
        $classes,
        create_function( '$class',
                 'return in_array( $class,
                      array( "current-menu-item", "current-menu-parent" ) );' )
    );
    return array_merge(
        $classes,
        (array)get_post_meta( $item->ID, '_menu_item_classes', true )
    );
}
//Deletes empty classes and removes the sub menu class
add_filter ('wp_nav_menu','strip_empty_classes');
function strip_empty_classes($menu) {
    $menu = preg_replace('/ class=""/','',$menu);
    return $menu;
}
/********* end CLEAN UP OUTPUT MENU *********/