Works with WooCommerce 2.6.x or below

get-order-detail-by-order-id-2_6.php

<?php

if (!function_exists('getOrderDetailById')) {

    function getOrderDetailById($id, $fields = null, $filter = array()) {

        if (is_wp_error($id))
            return $id;

        // Get the decimal precession
        $dp = isset($filter['dp']) ? intval($filter['dp']) : 2;
        $order = wc_get_order($id);
        $order_post = get_post($id);

        $order_data = array(
            'id' => $order->id,
            'order_number' => $order->get_order_number(),
            'created_at' => $order_post->post_date,
            'updated_at' => $order_post->post_modified,
            'completed_at' => !empty($order->completed_date) ? $order->completed_date : '',
            'status' => $order->get_status(),
            'currency' => $order->get_order_currency(),
            'total' => wc_format_decimal($order->get_total(), $dp),
            'subtotal' => wc_format_decimal($order->get_subtotal(), $dp),
            'total_line_items_quantity' => $order->get_item_count(),
            'total_tax' => wc_format_decimal($order->get_total_tax(), $dp),
            'total_shipping' => wc_format_decimal($order->get_total_shipping(), $dp),
            'cart_tax' => wc_format_decimal($order->get_cart_tax(), $dp),
            'shipping_tax' => wc_format_decimal($order->get_shipping_tax(), $dp),
            'total_discount' => wc_format_decimal($order->get_total_discount(), $dp),
            'shipping_methods' => $order->get_shipping_method(),
            'order_key' => $order->order_key,
            'payment_details' => array(
                'method_id' => $order->payment_method,
                'method_title' => $order->payment_method_title,
                'paid_at' => !empty($order->paid_date) ? $order->paid_date : '',
            ),
            'billing_address' => array(
                'first_name' => $order->billing_first_name,
                'last_name' => $order->billing_last_name,
                'company' => $order->billing_company,
                'address_1' => $order->billing_address_1,
                'address_2' => $order->billing_address_2,
                'city' => $order->billing_city,
                'state' => $order->billing_state,
                'formated_state' => WC()->countries->states[$order->billing_country][$order->billing_state], //human readable formated state name
                'postcode' => $order->billing_postcode,
                'country' => $order->billing_country,
                'formated_country' => WC()->countries->countries[$order->billing_country], //human readable formated country name
                'email' => $order->billing_email,
                'phone' => $order->billing_phone,
            ),
            'shipping_address' => array(
                'first_name' => $order->shipping_first_name,
                'last_name' => $order->shipping_last_name,
                'company' => $order->shipping_company,
                'address_1' => $order->shipping_address_1,
                'address_2' => $order->shipping_address_2,
                'city' => $order->shipping_city,
                'state' => $order->shipping_state,
                'formated_state' => WC()->countries->states[$order->shipping_country][$order->shipping_state], //human readable formated state name
                'postcode' => $order->shipping_postcode,
                'country' => $order->shipping_country,
                'formated_country' => WC()->countries->countries[$order->shipping_country] //human readable formated country name
            ),
            'note' => $order->customer_note,
            'customer_ip' => $order->customer_ip_address,
            'customer_user_agent' => $order->customer_user_agent,
            'customer_id' => $order->get_user_id(),
            'view_order_url' => $order->get_view_order_url(),
            'line_items' => array(),
            'shipping_lines' => array(),
            'tax_lines' => array(),
            'fee_lines' => array(),
            'coupon_lines' => array(),
        );

        //getting all line items
        foreach ($order->get_items() as $item_id => $item) {

            $product = $order->get_product_from_item($item);
            $product_id = null;
            $product_sku = null;

            // Check if the product exists.
            if (is_object($product)) {
                $product_id = !empty($product->variation_id) ? $product->variation_id : $product->id;
                $product_sku = $product->get_sku();
            }

            $meta = new WC_Order_Item_Meta($item, $product);

            $item_meta = array();

            $hideprefix = ( isset($filter['all_item_meta']) && $filter['all_item_meta'] === 'true' ) ? null : '_';

            foreach ($meta->get_formatted($hideprefix) as $meta_key => $formatted_meta) {
                $item_meta[] = array(
                    'key' => $formatted_meta['key'],
                    'label' => $formatted_meta['label'],
                    'value' => $formatted_meta['value'],
                );
            }

            $order_data['line_items'][] = array(
                'id' => $item_id,
                'subtotal' => wc_format_decimal($order->get_line_subtotal($item, false, false), $dp),
                'subtotal_tax' => wc_format_decimal($item['line_subtotal_tax'], $dp),
                'total' => wc_format_decimal($order->get_line_total($item, false, false), $dp),
                'total_tax' => wc_format_decimal($item['line_tax'], $dp),
                'price' => wc_format_decimal($order->get_item_total($item, false, false), $dp),
                'quantity' => wc_stock_amount($item['qty']),
                'tax_class' => (!empty($item['tax_class']) ) ? $item['tax_class'] : null,
                'name' => $item['name'],
                'product_id' => !empty($product->variation_id) ? $product->parent_id : $product_id,
                'variation_id' => !empty($product->variation_id) ? $product_id : 0,
                'sku' => $product_sku,
                'product_url' => get_permalink($product_id),
                'product_thumbnail_url' => wp_get_attachment_image_src(get_post_thumbnail_id($product_id), 'thumbnail', TRUE)[0],
                'meta' => $item_meta,
            );
        }

        //getting shipping
        foreach ($order->get_shipping_methods() as $shipping_item_id => $shipping_item) {

            $order_data['shipping_lines'][] = array(
                'id' => $shipping_item_id,
                'method_id' => $shipping_item['method_id'],
                'method_title' => $shipping_item['name'],
                'total' => wc_format_decimal($shipping_item['cost'], $dp),
            );
        }

        //getting taxes
        foreach ($order->get_tax_totals() as $tax_code => $tax) {
            $order_data['tax_lines'][] = array(
                'id' => $tax->id,
                'rate_id' => $tax->rate_id,
                'code' => $tax_code,
                'title' => $tax->label,
                'total' => wc_format_decimal($tax->amount, $dp),
                'compound' => (bool) $tax->is_compound,
            );
        }

        //getting fees
        foreach ($order->get_fees() as $fee_item_id => $fee_item) {
            $order_data['fee_lines'][] = array(
                'id' => $fee_item_id,
                'title' => $fee_item['name'],
                'tax_class' => (!empty($fee_item['tax_class']) ) ? $fee_item['tax_class'] : null,
                'total' => wc_format_decimal($order->get_line_total($fee_item), $dp),
                'total_tax' => wc_format_decimal($order->get_line_tax($fee_item), $dp),
            );
        }

        //getting coupons
        foreach ($order->get_items('coupon') as $coupon_item_id => $coupon_item) {
            $order_data['coupon_lines'][] = array(
                'id' => $coupon_item_id,
                'code' => $coupon_item['name'],
                'amount' => wc_format_decimal($coupon_item['discount_amount'], $dp),
            );
        }

        return array('order' => apply_filters('woocommerce_api_order_response', $order_data, $order, $fields));
    }

}