remove all items from cart exclude new

functions.php

<?php 
add_action( 'woocommerce_add_to_cart', 'remove_cart2',10 , 6 );
function remove_cart2($cart_item_key, $product_id, $quantity, $variation_id, $variation, $cart_item_data){
    global $woocommerce;
    

    if ($woocommerce->cart->get_cart_contents_count() != 0) {
        $cartQty = $woocommerce->cart->get_cart_item_quantities();
        $cartItems = $woocommerce->cart->cart_contents;
        // Check if desired product is in cart already
        if (array_key_exists($variation_id,$cartQty)) { // $product_id when buy Simple Product || $variation_id when buy Variable Product
            // Then first adjust its quantity
            foreach ($cartItems as $k => $v) {
                if ($cartItems[$k]['key'] == $cart_item_key) {
                    $woocommerce->cart->set_quantity($k, 1);
                }
            }
            // And only after that, set other products to zero quantity
            foreach ($cartItems as $k => $v) { 
                if ($cartItems[$k]['key'] != $cart_item_key) {
                    $woocommerce->cart->set_quantity($k, 0);
                }
            }
        }
    }
}