Woocommerce cart custom field error on update - wordpress

Question

I'm trying to add a custom field on each product on cart. I got the code from
WooCommerce: Add input field to every item in cart
but the update is not working. I tried to change the global $woocommerce to WC() but still it gives me 500 (Internal Server Error) on chrome console everytime I click update. heres the code:
cart.php:
<td class="product-url">
<?php
$html = sprintf( '<div class="url"><input type="text" name="cart[%s][url]" value="%s" size="4" title="Url" class="input-text url text" /></div>', $cart_item_key, esc_attr( $values['url'] ) );
echo $html;
?>
function.php (This is not a snippet so do not run):
// get from session your URL variable and add it to item
add_filter('woocommerce_get_cart_item_from_session', 'cart_item_from_session', 99, 3);
function cart_item_from_session( $data, $values, $key ) {
$data['url'] = isset( $values['url'] ) ? $values['url'] : '';
return $data;
}
// this one does the same as woocommerce_update_cart_action() in plugins\woocommerce\woocommerce-functions.php
// but with your URL variable
// this might not be the best way but it works
add_action( 'init', 'update_cart_action', 9);
function update_cart_action() {
global $woocommerce;
if ( ( ! empty( $_POST['update_cart'] ) || ! empty( $_POST['proceed'] ) ) && $woocommerce->verify_nonce('cart')) {
$cart_totals = isset( $_POST['cart'] ) ? $_POST['cart'] : '';
if ( sizeof( $woocommerce->cart->get_cart() ) > 0 ) {
foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values ) {
if ( isset( $cart_totals[ $cart_item_key ]['url'] ) ) {
$woocommerce->cart->cart_contents[ $cart_item_key ]['url'] = $cart_totals[ $cart_item_key ]['url'];
}
}
}
}
}
// this is in Order summary. It show Url variable under product name. Same place where Variations are shown.
add_filter( 'woocommerce_get_item_data', 'item_data', 10, 2 );
function item_data( $data, $cart_item ) {
if ( isset( $cart_item['url'] ) ) {
$data['url'] = array('name' => 'Url', 'value' => $cart_item['url']);
}
return $data;
}
// this adds Url as meta in Order for item
add_action ('woocommerce_add_order_item_meta', 'add_item_meta', 10, 2);
function add_item_meta( $item_id, $values ) {
woocommerce_add_order_item_meta( $item_id, 'Url', $values['url'] );
}