Linked Products as Options for OpenCart

The Linked Products as Options module combines separate product variant pages into logical groups and displays links between them as familiar options. Customers can select a color, size, storage capacity, material, or another attribute, while each variant remains a separate product with its own URL, price, special price, stock level, model, image, and SEO data.

This approach is suitable for stores where different colors, sizes, or configurations have already been created as separate products. The module does not replace or modify standard OpenCart options: it adds a separate mechanism for linking complete product pages.

Integration with the standard OpenCart theme is included, along with separate adaptations for OCTemplates Promo and OCTemplates Deals.

How the module works

The administrator selects one of the standard OpenCart fields as the product group identifier: UPC, EAN, JAN, ISBN, or MPN. Products with the same non-empty value in the selected field are automatically assigned to one group.

Option types are then created in the module, such as “Color,” “Size,” “Storage Capacity,” “Material,” or any other option required by the store. One or more product attributes can be selected for each type. If several attributes are selected, the module checks them in the specified order and uses the first non-empty value.

After synchronization, the available group variants appear on the product page. Clicking a value opens the corresponding product page, so every variant retains its own data, page address, and standard OpenCart product behavior.

Module features

• Automatically group products by the UPC, EAN, JAN, ISBN, or MPN field
• Use only exact matches of non-empty group identifiers
• Create any required number of option types
• Obtain option values from product attributes
• Use several attributes for one option type with configurable priority
• Display values as text buttons, HEX colors, or product images
• Configure multiple colors for a single value
• Configure the value sort order
• Create fully manual product groups
• Include or exclude products in an automatic group
• Set a manual option value for a specific product
• Control the display of out-of-stock products
• Index large catalogs in batches via CRON
• Automatically add changed products to the indexing queue through OpenCart Events
• Generate Schema.org structured data for product variants

Product group identifier

One of the standard product fields is used for automatic linking. The field is selected in the module settings and must contain the same value for every variant of the same model.

• UPC — Universal Product Code
• EAN — European Article Number
• JAN — Japanese Article Number
• ISBN — International Standard Book Number
• MPN — model or group code assigned by the manufacturer or administrator

For example, six separate Samsung Galaxy product pages may have different models, colors, storage capacities, prices, and stock levels, but the same group MPN. After indexing, the module links them and displays color and storage as navigation between variants.

Option types and attributes

Option type names are not predefined or restricted. The store creates the variants required for its catalog: color, size, storage, material, style, length, configuration, or any other attribute.

Several attributes can be assigned to one option type. This is useful when the same information is stored under different names in different categories, such as “Color,” “Body Color,” or “Primary Color.” The attribute order determines the priority in which they are checked.

• Text — values are displayed as compact buttons
• Color — values are displayed as a HEX palette
• Image — the main image of the corresponding product is used

The module does not create separate images for option values. Image mode uses the existing main product image and the thumbnail dimensions configured in the module.

HEX palette and value sorting

After indexing, the module collects the detected attribute values on a separate tab. A sort order can be set for every value, while one or more HEX codes can be assigned to colors.

If a value consists of several colors, the module creates a multicolor swatch. Configured HEX codes and sorting are retained independently of the current display type. Switching an option from color to image and back does not remove the previously configured palette.

Display on the product page

• The current option value is highlighted and is not an active link
• Text values are displayed as buttons
• Colors are displayed as solid or multicolor swatches
• The main image of the corresponding product is used in image mode
• The product name is available on hover in image mode
• Out-of-stock products can be displayed, disabled, or completely hidden
• Unavailable values have a separate visual style

When a value is selected, the customer is taken to the separate page of the corresponding product. The module does not replace the price, stock, or image through JavaScript, so the page always uses current standard OpenCart product data.

Manual groups

Automatic mode can be supplemented with manual management. A separate page provides a list of all created groups with filtering, sorting, and pagination.

• Search by group name or identifier
• Search for a group by product, model, or SKU
• Filter automatic, manual, and mixed groups
• Create a new manual group
• Add products using autocomplete
• Manually sort products within a group
• Set manual option values separately for each language
• Disable an individual group
• Lock an automatic group

A manual value takes priority over an automatically obtained attribute value. This makes it possible to add a product with incomplete data to a group without changing its standard attributes.

Clearing groups

The module provides three separate clearing modes:

• Automatic groups — clears the automatic index and groups created by synchronization
• Manual groups — removes groups created manually by the administrator
• All groups — completely clears the module’s automatic and manual groups

Indexing and CRON

For fast storefront performance, the module builds its own relationship index in advance. Data is processed in batches, allowing the module to be used with large catalogs without a long-running query when a product page is opened.

• Configurable number of products per batch
• Manual full synchronization from the administration panel
• Secret-key-protected URL for CRON
• Ready-to-use crontab command
• Indexing status, progress, and statistics

The current index remains operational during full synchronization. The new data generation becomes active only after the rebuild completes successfully. Customers do not see partially populated groups while the catalog is being updated.

Automatic updates after product changes

The module uses standard OpenCart Events. After a product is added, edited, or deleted, its identifier is placed in a queue. The next CRON run updates only the changed products and their related groups.

Direct SQL queries and some third-party imports may not trigger OpenCart Events. A full synchronization is recommended after a bulk direct import or changes to group identifiers.

SEO and structured data

A corresponding Schema.org property can be selected for each option type. If no property is selected, the module does not add structured data for that option.

• ProductGroup — a logical group of product variants
• productGroupID — the product group identifier
• hasVariant and isVariantOf — the relationship between the group and its variants
• variesBy — the list of properties by which products differ
• color — color
• size — size
• material — material
• pattern — pattern
• suggestedAge — suggested age
• suggestedGender — suggested gender
• additionalProperty — another product attribute

For the standard theme, the module generates its own structured data block. The OCTemplates Promo and Deals adaptations also integrate the variant relationship into the native product structured data of the corresponding theme.

Performance

• Separate index tables with database indexes for primary queries
• Batch loading of product attributes
• Batch insertion of index records
• Active data is not cleared before full synchronization is complete
• Incremental updates for changed products
• Option type settings cached through the standard OpenCart cache
• No external API requests on the product page

Multilingual and multistore support

Group names, option type names, and manual values can be specified separately for each language. When displaying variants, the module respects the current OpenCart language and store and does not show products that are not assigned to the current store.

The module administration interface is localized in Ukrainian, English, and Russian.

Theme integration

• Default — support is included in the main package
• OCTemplates Promo — a separate adaptation package with its own Twig template and CSS
• OCTemplates Deals — a separate adaptation package with its own Twig template and CSS

For Promo or Deals, install only the adaptation that matches the active theme. The main module must always be installed.

Open source code and independence

The module code is not encrypted or obfuscated. All PHP, Twig, JavaScript, CSS, and XML files are available for review and modification.

The module does not connect to third-party resources, external APIs, or remote servers and does not require third-party libraries or system services. Product processing, group building, caching, and variant block generation are performed directly on the website.

Thanks to a separate Twig template, CSS file, and targeted OCMOD integration, the module can be adapted to other OpenCart themes without changing its core logic. For a custom product page, it is usually sufficient to prepare a separate adaptation with the appropriate output position and styles for the active theme.

Installation

1. Perform a clean installation of the main package through Extensions / Installer
2. If OCTemplates Promo or Deals is used, upload the corresponding adaptation package
3. Go to Extensions / Modifications and click Refresh
4. Go to Extensions / Extensions
5. Select the Modules extension type
6. Find Linked Products as Options and click Install
7. Open the module settings
8. Select the group identifier field and create the required option types
9. Run a full synchronization
10. Add the protected URL to your CRON scheduler

The module does not modify OpenCart core files directly. Integration is performed through standard OpenCart Events and OCMOD.

Important notes

• To create groups automatically, at least two enabled products must have the same non-empty value in the selected UPC, EAN, JAN, ISBN, or MPN field.
• A full synchronization must be performed after changing the group identifier field, the attribute configuration, or running a bulk direct import.
• Regular CRON runs process the changed-product queue and continue an unfinished full synchronization. For a small catalog, synchronization can also be started manually from the administration panel.
• Uninstalling the module with the Uninstall button removes the tables, index, automatic and manual groups, palettes, and other value settings created by the module. Products, attributes, and standard OpenCart data are not removed.

License

The license covers one domain and its subdomains.