[Add Cart / Checkout Field Woocommerce]

cart.php

<form class=" woocommerce-cart-form">
  ...
  <input type="hidden" id="cart_extra_option" name="cart_extra_option" value="value" >
  <input type="hidden" id="cart_total_price" name="cart_total_price" value="value">
  ...
</form>

functions.php

// MAKE FIELDS
add_action('woocommerce_before_order_notes', 'wps_add_select_checkout_field');
function wps_add_select_checkout_field($checkout)
{
    woocommerce_form_field('cart_extra_option', array(
        'type'          => 'text',
        'class'         => array( 'wps-drop' ),
        'label'         => __('cart_extra_option'),
        'options'       => $options,
    ), $checkout->get_value('cart_extra_option'));

    woocommerce_form_field('cart_total_price', array(
            'type'          => 'text',
            'class'         => array( 'wps-drop' ),
            'label'         => __('cart_total_price'),
            'options'       => $options,
    ), $checkout->get_value('cart_total_price'));
}

//SAVE FIELDS
add_action('woocommerce_checkout_update_order_meta', 'bbloomer_save_new_checkout_field');

function bbloomer_save_new_checkout_field($order_id)
{
    if ($_POST['cart_extra_option']) {
        update_post_meta($order_id, '_cart_extra_option', esc_attr($_POST['cart_extra_option']));
    }#
    if ($_POST['cart_total_price']) {
        update_post_meta($order_id, '_cart_total_price', esc_attr($_POST['cart_total_price']));
    }
}

//SHOW FIELDS ON ADMIN
add_action('woocommerce_admin_order_data_after_billing_address', 'bbloomer_show_new_checkout_field_order', 10, 1);

function bbloomer_show_new_checkout_field_order($order)
{
    $order_id = $order->get_id();
    if (get_post_meta($order_id, '_cart_extra_option', true)) {
        echo '<p><strong>cart_extra_option:</strong> ' . get_post_meta($order_id, '_cart_extra_option', true) . '</p>';
    }
    if (get_post_meta($order_id, '_cart_total_price', true)) {
        echo '<p><strong>cart_total_price:</strong> ' . get_post_meta($order_id, '_cart_total_price', true) . '</p>';
    }
}