OpenCart Multi-Warehouse Setup

OpenCart Multi-Warehouse Setup

Multi-warehouse in OpenCart allows dividing product inventory across multiple physical or logical storage points — office, supplier warehouse, dropshipping partner, regional hub. Without this setup, a store with multiple supply sources loses inventory accuracy and complicates logistics.

What is Multi-Warehouse in OpenCart

Standard OpenCart installation stores inventory in single oc_product table (quantity + subtract). To work with multiple warehouses need module adding oc_location, oc_product_location tables and logic for deduction on order.

Popular solutions:

• Journal3 Warehouse — built into Journal3 theme
• Multi Warehouse Pro from Opencart.com — official extension
• XLDevelopment module — flexible warehouse priority setup
• Custom development via Events + Model override

Solution Architecture

Basic schema for custom implementation:

CREATE TABLE oc_location (
  location_id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(128),
  address TEXT,
  status TINYINT(1)
);

CREATE TABLE oc_product_to_location (
  product_id INT,
  location_id INT,
  quantity INT DEFAULT 0,
  PRIMARY KEY (product_id, location_id)
);

On order placement catalog/model/checkout/order/addOrder/after event triggers custom observer deducting inventory from needed warehouse by priority rule (closest to buyer, first non-empty, product-specific warehouse).

Setup via Extension

Step 1 — Install module

Upload via admin > Extensions > Installer. Module registers events via oc_event:

// install.php
$this->model_setting_event->addEvent([
    'code'    => 'multi_warehouse',
    'trigger' => 'catalog/model/checkout/order/addOrder/after',
    'action'  => 'extension/multi_warehouse/model/warehouse/subtractStock',
    'status'  => 1,
    'sort_order' => 1
]);

Step 2 — Create warehouses

In Extensions > Multi Warehouse > Locations create warehouses: name, address, priority, shipping zone mapping.

Step 3 — Distribute products

Product card gets "Warehouses" tab. For each warehouse specify available quantity. With subtract enabled system works with aggregated inventory.

Step 4 — Warehouse selection rules

Deduction strategies:

• FIFO by priority — takes from warehouse with lowest priority
• Closest to buyer — by shipping zone mapping
• Product-specific — hard tie to warehouse
• Mixed — deducts from multiple warehouses on deficiency (split fulfillment)

Supplier Integration

For dropshipping or VMI inventory updates via API:

// Update warehouse stock via custom API endpoint
// admin/controller/api/warehouse.php

public function updateStock(): void {
    $json = [];
    $location_id = (int)$this->request->post['location_id'];
    $updates = $this->request->post['products']; // [{product_id, quantity}]

    foreach ($updates as $item) {
        $this->model_extension_warehouse->setLocationStock(
            (int)$item['product_id'],
            $location_id,
            (int)$item['quantity']
        );
    }
    $json['success'] = count($updates) . ' products updated';
    $this->response->addHeader('Content-Type: application/json');
    $this->response->setOutput(json_encode($json));
}

Supplier makes POST /index.php?route=api/warehouse/updateStock with token in header — inventory updates without admin access.

Display on Frontend

By default customer sees total inventory. Can show availability by warehouse:

{% if product.locations %}
  <ul class="warehouse-availability">
  {% for loc in product.locations %}
    <li>{{ loc.name }}:
      {% if loc.quantity > 0 %}in stock ({{ loc.quantity }} units)
      {% else %}out of stock{% endif %}
    </li>
  {% endfor %}
  </ul>
{% endif %}

Relevant for B2B stores where buyer selects pickup warehouse.

Reservation and Returns

Important — reserve inventory on payment, not on order creation. Module must handle statuses:

Configure events on catalog/model/checkout/order/addOrderHistory/after.

Reporting

Useful SQL queries for inventory control:

-- Inventory by warehouses
SELECT l.name AS location, p.model, ptl.quantity
FROM oc_product_to_location ptl
JOIN oc_location l ON l.location_id = ptl.location_id
JOIN oc_product p ON p.product_id = ptl.product_id
WHERE ptl.quantity < 5
ORDER BY l.name, p.model;

-- Movement by warehouse for period
SELECT DATE(oh.date_added), SUM(op.quantity)
FROM oc_order_history oh
JOIN oc_order_product op ON op.order_id = oh.order_id
WHERE oh.order_status_id = 2 -- Processing
  AND oh.date_added BETWEEN '2025-01-01' AND '2025-01-31'
GROUP BY DATE(oh.date_added);

Timeline and Effort

Setting up ready module with 2–3 warehouses: 2–3 days. Custom development from scratch (priorities, supplier API, split fulfillment): 1–2 weeks. Integration with external WMS (1C, MoyaSklad) adds 3–5 days for data mapping and testing.