WP Woocommerce - Clear cart before adding new one

functions.php

<?php

// clear cart before adding new one
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->is_empty() )
        WC()->cart->empty_cart();
    return $passed;
}