访问时自动添加产品到购物车

/*
 * Add item to cart on visit
 */
function add_product_to_cart() {
  if ( ! is_admin() ) {
    global $woocommerce;
    $product_id = 64;
    $found = false;
    https://check if product already in cart
    if ( sizeof( $woocommerce->cart->get_cart() ) > 0 ) {
      foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values ) {
        $_product = $values['data'];
        if ( $_product->id == $product_id )
          $found = true;
      }
      https:// if product not found, add it
      if ( ! $found )
        $woocommerce->cart->add_to_cart( $product_id );
    } else {
      https:// if no products in cart, add it
      $woocommerce->cart->add_to_cart( $product_id );
    }
  }
}
add_action( 'init', 'add_product_to_cart' );

在哪里添加此代码？

将PHP代码放在主题或子主题functions.php文件的底部。