Add a fixed surcharge to your cart and checkout based on array of product IDs in cart –– WooCommerce

functions.php

<?php
/**
 * Add a fixed surcharge to your cart and checkout based on array of
 * product ids in cart.
 *
 * @author Blake Wilson
 * @link https://gist.github.com/blakewilson/1d1be3ed68526dc12a5cb28d44cb6316
 * @license MIT
 * @license https://opensource.org/licenses/MIT
 *
 * @var array   $products_array Should be an array of WooCommerce product IDs 
 * @var integer $fixed_fee      The fee amount as an integer 
 * @var string  $surcharge_name The name of the surcharge, localized for WordPress
 */
function themeprefix_woocommerce_surcharge() {
  global $woocommerce;

  if ( is_admin() && ! defined( 'DOING_AJAX' ) )
    return;

  /**
   * Setup the array of products that have a surcharge
   */
  $products_array = array( '99', '572' );

  /**
   * Our fee amount
   */
  $fixed_fee = 2.00;

  /**
   * The surcharge name
   */
  $surcharge_name = __( 'Surcharge', 'text-domain' );

  /**
   * Loop through the cart looking for products that match the ids of the
   * $products_array array
   */
  foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values ) {
    if ( in_array( $values['product_id'], $products_array ) ) {
      $woocommerce->cart->add_fee( $surcharge_name, $fixed_fee, true, '' );
    }
  }
}
add_action( 'woocommerce_cart_calculate_fees', 'themeprefix_woocommerce_surcharge' );
?>