Save custom product fields to cart/checkout/order

I found a solution and I’ll break it down here:

Step 1 – Add custom fields to product

add_action( 'woocommerce_after_variations_table', 'woo_show_some_text', 20 );
if(!function_exists('woo_show_some_text')){
    function woo_show_some_text() {
        echo '
        <div class="customSelection">
        <input type="hidden" name="combination" value="">
        <input type="hidden" name="totalCombination" value="">
        <div class="combination"></div>
        <label><input onkeypress="return onlyNumberKey(event)" value="0" class="numeric combinationFormula" type="number" placeholder="0" min="0" step="1" name="standard"> Standard</label>
        <label><input onkeypress="return onlyNumberKey(event)" value="0" class="numeric combinationFormula" type="number" placeholder="0" min="0" step="1" name="ministandard"> Mini Standard</label>
        <label><input onkeypress="return onlyNumberKey(event)" value="0" class="numeric combinationFormula" type="number" placeholder="0" min="0" step="1" name="offset"> Offset</label>
        <label><input onkeypress="return onlyNumberKey(event)" value="0" class="numeric combinationFormula" type="number" placeholder="0" min="0" step="1" name="wand"> Wand</label>
        </div>
        ';
    }
}

Step 2 – save custom fields to cart

add_filter('woocommerce_add_cart_item_data','wdm_add_item_data',10,3);
function wdm_add_item_data($cart_item_data, $product_id, $variation_id){
    if(isset($_REQUEST['standard'])){
        $cart_item_data['standard'] = sanitize_text_field($_REQUEST['standard']);
    }
	if(isset($_REQUEST['ministandard'])){
        $cart_item_data['ministandard'] = sanitize_text_field($_REQUEST['ministandard']);
    }
	if(isset($_REQUEST['offset'])){
        $cart_item_data['offset'] = sanitize_text_field($_REQUEST['offset']);
    }
	if(isset($_REQUEST['wand'])){
        $cart_item_data['wand'] = sanitize_text_field($_REQUEST['wand']);
    }
    return $cart_item_data;
}

Step 3– display custom fields on cart page

add_filter('woocommerce_get_item_data','wdm_add_item_meta',10,2);
function wdm_add_item_meta($item_data, $cart_item){
    if(array_key_exists('standard', $cart_item)){
        $custom_details = $cart_item['standard'];
        $item_data[] = array(
            'key'   => 'Standard',
            'value' => $custom_details
        );
    }
    if(array_key_exists('ministandard', $cart_item)){
        $custom_details = $cart_item['ministandard'];
        $item_data[] = array(
            'key'   => 'Mini Standard',
            'value' => $custom_details
        );
    }
    if(array_key_exists('offset', $cart_item)){
        $custom_details = $cart_item['offset'];
        $item_data[] = array(
            'key'   => 'Offset',
            'value' => $custom_details
        );
    }
    if(array_key_exists('wand', $cart_item)){
        $custom_details = $cart_item['wand'];
        $item_data[] = array(
            'key'   => 'Wand',
            'value' => $custom_details
        );
    }
    return $item_data;
}

Step 4 – display custom fields on order details

add_action( 'woocommerce_checkout_create_order_line_item', 'wdm_add_custom_order_line_item_meta',10,4 );
function wdm_add_custom_order_line_item_meta($item, $cart_item_key, $values, $order){
    if(array_key_exists('standard', $values)){
        $item->add_meta_data('Standard',$values['standard']);
    }
    if(array_key_exists('ministandard', $values)){
        $item->add_meta_data('Mini Standard',$values['ministandard']);
    }
    if(array_key_exists('offset', $values)){
        $item->add_meta_data('Offset',$values['offset']);
    }
    if(array_key_exists('wand', $values)){
        $item->add_meta_data('Wand',$values['wand']);
    }
}

I wish WooCommerce can make this easier 🙂 Solution was found on this website