Clear Woocommerce cart when sending multiple items by url - php

Question

I need the Woocommerce cart to be cleaned in case I send more than four items to it via url.
I came up with this code, but it only cleans the cart if there are already five items in it.
//in functions.php
add_filter( 'woocommerce_add_to_cart_validation', 'remove_cart_item_before_add_to_cart', 20, 3 );
function remove_cart_item_before_add_to_cart( $passed, $product_id, $quantity ) {
if( WC()->cart->get_cart_contents_count() >= 5 )
WC()->cart->empty_cart();
return $passed;
}
Another problem is that, even the code above that is not useful to me, does not work if I add multiple courses via url, as in:
https://exemple.net/cart?fill_cart=100,101,102,103,104,105,106
That is, the code in functions.php only works from the website, and not by url.
All I need is clear the cart when sending more than 4 items by url.
I prefer a solution in PHP, but a JS solution will do. Thanks for who can help me.

Answer 1

I found a solution using the free plugin Cart links for WooCommerce, and making a few change in its code.
I will describe below what I did:
1) To start install the plugin, this will allow you to add products using the fill_cart parameter in url (as described in my question)
2) edit the plugin file soft79-cart-links-for-woocommerce.php found at: yoursite/wp-content/plugins/soft79-cart-links-for-woocommerce/
3) go to line 141 or find the declaration of the method fill_cart
Inside the fill_cart method uncomment (or add) the code to clean the cart:
public function fill_cart( $fill_string ) {
$original_notices = wc_get_notices();
wc_clear_notices();
////Clear the cart
//WC()->cart->empty_cart(); <-- uncomment here!
Save the file. Now any new items that arrive via url must clean the cart first.