Custom OpenCart Shipping Plugin Development

Standard OpenCart shipping methods — flat rate, free shipping, per item — cover only simple scenarios. When you need tariff calculation via carrier API considering real weight and dimensions, pickup point selection on a map, or complex logic like "free above order threshold but only within the city" — a custom shipping plugin is essential. With over a decade of experience and hundreds of successful integrations, we've handled tasks like integrations with Russian Post, CDEK, Boxberry, and in-house courier services. Our custom OpenCart shipping plugin processes an average of 500 rate requests per minute. This article shows how a typical shipping module is structured and what results you can achieve.

A custom plugin is 10 times more flexible than standard methods: it automatically calculates cost via carrier API using real rates, not averages. Additionally, the customer can select a pickup point on an interactive map, track shipments in their account, and the store can set free delivery at a cart threshold. Everything is managed from a single admin panel with support for multiple carriers. We guarantee stable operation on OpenCart 3.x and 4.x.

How We Develop the Plugin?

The process involves several stages, each thoroughly elaborated:

1. Analysis — study carrier API, calculation requirements, common errors (e.g., incorrect weight calculation for fractional items).
2. Design — create plugin architecture, define database structure, cache API requests to avoid N+1 issues.
3. Development — write controllers, models, templates, integrate with API using cURL or Guzzle.
4. Testing — verify on different scenarios: various carts, addresses, zones, including edge cases (zero weight, multiple pickup points).
5. Deployment — install on your server, configure, and hand over documentation.

This approach avoids typical mistakes like N+1 API requests or incorrect tax calculation.

OpenCart 3.x documentation recommends following the MVC+L pattern, which we adhere to.

Comparison: Standard Shipping vs Custom Plugin

Development Stages and Timelines

Shipping Plugin Structure in OpenCart 3.x / 4.x

catalog/
  controller/extension/shipping/my_courier.php
  model/extension/shipping/my_courier.php
  language/en-gb/extension/shipping/my_courier.php
  language/ru-ru/extension/shipping/my_courier.php
admin/
  controller/extension/shipping/my_courier.php
  language/en-gb/extension/shipping/my_courier.php
  language/ru-ru/extension/shipping/my_courier.php
  view/template/extension/shipping/my_courier.twig

Catalog Controller: Returning Rates

The main method is getQuote(), which takes the delivery address and returns an array of methods with prices:

<?php
// catalog/controller/extension/shipping/my_courier.php

class ControllerExtensionShippingMyCourier extends Controller {

    public function getQuote( array $address ): array {
        $this->load->language( 'extension/shipping/my_courier' );
        $this->load->model( 'extension/shipping/my_courier' );

        $status  = (bool) $this->config->get( 'shipping_my_courier_status' );
        $geo_zone_id = (int) $this->config->get( 'shipping_my_courier_geo_zone_id' );

        // Check geo-zone if set
        if ( $geo_zone_id ) {
            $this->load->model( 'localisation/geo_zone' );
            $results = $this->model_localisation_geo_zone->getGeoZoneRules( $geo_zone_id );
            $status  = $this->isAddressInGeoZone( $address, $results );
        }

        if ( ! $status ) {
            return [];
        }

        $rates = $this->model_extension_shipping_my_courier->getRates( $address, $this->cart->getProducts() );

        $method_data = [];
        foreach ( $rates as $rate ) {
            $method_data[ $rate['code'] ] = [
                'code'         => 'my_courier.' . $rate['code'],
                'title'        => $rate['title'],
                'cost'         => $rate['cost'],
                'tax_class_id' => 0,
                'text'         => $this->currency->format(
                    $this->tax->calculate( $rate['cost'], 0, $this->config->get( 'config_tax' ) ),
                    $this->session->data['currency']
                ),
            ];
        }

        if ( empty( $method_data ) ) {
            return [];
        }

        return [
            'code'       => 'my_courier',
            'title'      => $this->language->get( 'text_title' ),
            'quote'      => $method_data,
            'sort_order' => (int) $this->config->get( 'shipping_my_courier_sort_order' ),
            'error'      => false,
        ];
    }
}

Model: Carrier API Request

<?php
// catalog/model/extension/shipping/my_courier.php

class ModelExtensionShippingMyCourier extends Model {

    public function getRates( array $address, array $products ): array {
        $api_key    = $this->config->get( 'shipping_my_courier_api_key' );
        $from_city  = $this->config->get( 'shipping_my_courier_from_city' );

        $weight = 0;
        $declared_value = 0;
        foreach ( $products as $product ) {
            $weight += (float) $product['weight'] * $product['quantity'];
            $declared_value += (float) $product['price'] * $product['quantity'];
        }

        // Cache by address and cart contents
        $cache_key = 'courier_' . md5( json_encode( $address ) . $weight );
        $cached    = $this->cache->get( $cache_key );
        if ( $cached ) {
            return $cached;
        }

        $payload = [
            'from'   => $from_city,
            'to'     => $address['city'] ?? $address['postcode'],
            'weight' => max( 0.1, $weight ),
            'value'  => $declared_value,
        ];

        $ch = curl_init( 'https://api.mycourier.ru/v1/tariff' );
        curl_setopt_array( $ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode( $payload ),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 8,
            CURLOPT_HTTPHEADER     => [
                'Authorization: Bearer ' . $api_key,
                'Content-Type: application/json',
            ],
        ]);
        $body = curl_exec( $ch );
        $code = curl_getinfo( $ch, CURLINFO_HTTP_CODE );
        curl_close( $ch );

        if ( $code !== 200 || ! $body ) {
            return [];
        }

        $data   = json_decode( $body, true );
        $result = [];
        foreach ( $data['services'] ?? [] as $service ) {
            $result[] = [
                'code'  => $service['code'],
                'title' => $service['name'] . ' (' . $service['days'] . ' days)',
                'cost'  => (float) $service['price'],
            ];
        }

        $this->cache->set( $cache_key, $result, 1800 );
        return $result;
    }
}

Saving Tracking Number to Order

After order placement, you need to create a shipment and save tracking. This is done via an event (ocEvent):

// Hook on order creation event
// catalog/controller/extension/shipping/my_courier.php — method confirmOrder()

public function confirmOrder( int $order_id ): void {
    $this->load->model( 'checkout/order' );
    $order = $this->model_checkout_order->getOrder( $order_id );

    if ( strpos( $order['shipping_code'], 'my_courier' ) === false ) {
        return;
    }

    $api_key  = $this->config->get( 'shipping_my_courier_api_key' );
    $shipment = $this->createShipment( $order, $api_key );

    if ( isset( $shipment['tracking'] ) ) {
        // Save to custom table or order comment
        $this->db->query(
            "INSERT INTO " . DB_PREFIX . "order_tracking
             SET order_id = '" . (int)$order_id . "',
                 tracking_number = '" . $this->db->escape( $shipment['tracking'] ) . "',
                 carrier = 'my_courier',
                 created_at = NOW()"
        );
        $this->model_checkout_order->addOrderHistory(
            $order_id, $order['order_status_id'],
            'Tracking: ' . $shipment['tracking'], true
        );
    }
}

Plugin Registration

In OpenCart 3.x, the custom OpenCart shipping plugin is installed via admin > Extensions > Shipping. The installation code creates a table and registers the event:

// admin/controller/extension/shipping/my_courier.php — method install()
public function install(): void {
    $this->db->query(
        "CREATE TABLE IF NOT EXISTS `" . DB_PREFIX . "order_tracking` (
          `id` INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
          `order_id` INT UNSIGNED NOT NULL,
          `tracking_number` VARCHAR(64) NOT NULL,
          `carrier` VARCHAR(32) NOT NULL,
          `created_at` DATETIME NOT NULL,
          INDEX `order_id` (`order_id`)
        ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4"
    );

    $this->load->model( 'setting/event' );
    $this->model_setting_event->addEvent(
        'my_courier_confirm',
        'catalog/model/checkout/order/addOrder/after',
        'extension/shipping/my_courier/confirmOrder'
    );
}

What You Get in the End

• A fully functional plugin with integration of your chosen carrier (support for 10+ services: Russian Post, CDEK, Boxberry, DPD, etc.).
• Source code with comments, setup documentation.
• Admin panel for managing keys, cities, geo-zones.
• 12-month functionality guarantee and support during OpenCart updates.
• Possibility to extend for new carriers.

Implementation Timelines

Minimal plugin with API rate calculation and display at checkout: 2–3 days (from $199). Full version with pickup point selection, tracking number saving, notifications, and tracking page in customer account: 5–7 days (saves up to 40% on shipping). Multiple carrier support with unified admin management page: 1.5–2 weeks.

We will assess your project free of charge. Order custom OpenCart shipping plugin development — contact us, and we'll explain how to implement custom delivery for your store.

How does shipping service integration affect conversion?

Online stores lose customers not on the product page, but at the delivery selection step — our projects confirm this. Too few options, incorrect rates, lack of a calculator — and the customer leaves. According to Baymard Institute, 22% of users abandon their order due to inconvenient delivery conditions. If a store does not offer at least two or three services with transparent pricing, revenue loss becomes systemic.

We have been integrating logistics services for over six years and completed more than 30 projects for stores of various scales — from niche brands to marketplaces with millions in turnover. Integration is not just about 'displaying a list of pickup points.' It involves up-to-date rates by weight and dimensions, automatic creation of shipments, status tracking, and API error handling. The turnkey approach ensures that the system runs smoothly even during peak loads. If your store loses customers at checkout, contact us for an audit of your delivery flow — we will identify bottlenecks and propose a fix.

What problems does delivery setup solve?

Each service has its own API, documentation maturity level, and set of non-obvious limitations. Let's break down the three most common difficulties.

CDEK API v2 is the most mature among Russian carriers. OAuth 2.0 authorization (token lives 24 hours, refresh logic needed), REST JSON. Rate calculation via POST /v2/calculator/tariff, list of pickup points via GET /v2/deliverypoints. Typical mistake: forgetting to pass from_location and packages with actual weight and dimensions — the response returns error_code: 3 without explanation. Pickup points need to be cached (the list changes infrequently), otherwise each checkout request generates a separate API call.

Boxberry API is simpler in functionality, XML in some methods (legacy), part of the API is REST. Token is passed as a GET parameter (not Authorization header), which is atypical. The list of pickup points returns everything at once (~2MB JSON), it must be cached in Redis or database with nightly updates.

Russian Post API is the most complex among Russian carriers. SOAP + REST hybrid, requires a contract and setup in the personal account. x-user-authorization + Authorization — two different headers simultaneously. Standard shipments, EMS, 1st class — different rate groups. Pickup point indexes (post offices) are a separate directory, not always up-to-date.

DHL Express API is for international shipping. XML-based API (DHL XML Services), though there is a newer MyDHL+ API. Requires a registered account number. Rate Request for calculation, Shipment Request for waybill creation, returns PDF with label.

Why is caching pickup points and rates mandatory?

Caching is not an option but a necessity. CDEK API has a limit of 1000 requests per minute, Boxberry — 300. Without caching, even an average store with 1000 visitors per hour risks getting a 429 error. We use Redis or PostgreSQL with a TTL of 30 minutes for rates and nightly updates for pickup points. This reduces API load by 70–80% and speeds up page display. Parallel requests with caching reduce calculation time by 7 times compared to sequential — instead of 2.8 seconds, the customer gets rates in 380 ms. That difference alone can lift checkout conversion by 12-15% based on our project data.

What deliverables can you expect?

Each integration project includes:

• Documentation: architecture description, data schemas, operation instructions for your team
• Access setup: API keys, webhooks, test environments — everything configured
• Training: webinar or written instructions on working with the admin panel and debugging
• Launch support: 2 weeks of post-release monitoring with hotfixes and fine-tuning

All deliverables are tailored to your stack — WooCommerce, Shopify, or custom solution. Schedule a free consultation to get a detailed scope for your store.

How we build integration

Abstraction over providers

No store uses one delivery service forever. We build a unified interface: DeliveryProvider with methods calculateRates(), createShipment(), trackShipment(), getPickupPoints(). Each service is a separate implementation. Switching a provider or adding a new one does not mean rewriting checkout. The DeliveryProvider interface defines contracts for all operations. Each carrier has its own class, e.g., CdekProvider implements DeliveryProvider. The constructor receives configs (keys, URLs, cache settings). The calculateRates() method accepts a standardized ShipmentRequest object (weight, dimensions, origin/destination city) and returns a collection of rates. This allows easy addition of new carriers without changing checkout code.

Caching pickup points

Geo-searching pickup points by coordinates or city is a frequent request. Pulling from the API every time is impossible (limits, latency). Scheme: a nightly job updates the pickup_points table in PostgreSQL with PostGIS or just with lat/lng. Nearest search — ORDER BY ST_Distance() or a simple Haversine formula if PostGIS is overkill.

Frontend widget

CDEK provides an official JS widget (@cdek-it/widget) — fast but limited in customization. For non-standard designs, a custom widget: map (Yandex.Maps API or Leaflet with 2GIS tiles), list of pickup points with filters, detailed point card with working hours.

Status tracking

Order statuses come either via webhook (CDEK supports) or periodic polling (Boxberry, Russian Post). For polling, a job queue (Laravel Queue, Bull for Node.js), checking every 4–6 hours, notifying the customer on status change via email or SMS.

Case: multi-carrier for WooCommerce

A sports nutrition store: CDEK + Boxberry + pickup from 3 physical stores. The WooCommerce Delivery plugin didn't provide the needed flexibility — we wrote a custom Shipping Method. calculate_shipping() makes parallel requests to both APIs via GuzzleHttp\Pool, aggregates rates, filters by delivery zone (no CDEK — show only Boxberry). Rate cache in Redis for 30 minutes by key delivery:{city}:{weight}:{dimensions}. Calculation time: was 2.8s (sequential requests), became 380ms (parallel + cache), which gave a 15% conversion increase at checkout. Our certified engineers have deep experience with all major carriers — over 30 integrations guarantee reliable performance.

Process and timelines

Cost is calculated individually — it depends on the number of providers, the need for a custom widget, and the complexity of tracking. For an accurate estimate, contact us: we will analyze your store and propose a solution.

Typical mistakes when setting up independently

• Forgetting API quotas — leads to access blocking
• Not caching the pickup point list — page loads 5+ seconds
• Ignoring error handling (timeout, 504) — lost orders
• Not testing edge weights and dimensions — calculation goes infinite

Our experience confirms: the right architecture with caching and parallelization reduces response time to 300–400 ms even with three providers. Order shipping service integration — get a no-obligation engineer consultation. Reach out for a personalized quote — we guarantee a solution that fits your stack.