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Extensibility and modularity


Product extensibility describes how easy it is to expand a product’s feature set. An extensible product has been designed from its earliest stages for customization and enhancement. Extensible products are designed for ease in expanding your installation’s feature set, enriching current features, and integrating with third-party software.

Maximizing extensibility has been our goal through all aspects of Magento development. Core tasks such as shipping are packaged as discrete modules, and you expand your features by installing modules that you either buy from third-party vendors or create yourself. While logic specific to each shipping carrier is packaged in a discrete module, you can easily add or delete shipping providers by simply adding or deleting modules. The Magento Framework provides common logic to control routing and other core application functions.

What makes a product extensible?

Magento extensibility describes the product’s built-in ability for developers and merchants to routinely extend their storefront’s capabilities as their business grows.

The following factors significantly affect extensibility.

Architectural principles that guide product structure

Central to the Magento model of software development is the practice of replacing or extending core code rather than editing it. This strategy supports your efforts to maintain the integrity of the tested code we provide while still extensively customizing your storefront.

Reliance on known architectural and programming structures helps PHP developers orient themselves to the specific development issues that affect coding in a particular product ecosystem. This can reduce the learning curve for new Magento developers.

Design patterns are time-tested, widely recognized software architecture constructs. Magento product architecture incorporates many well known patterns, but Model-View-Controller (MVC) holds particular interest for extension developers.


The concept of the module is the heart of Magento extension development, and modular design of software components (in particular, modules, themes, and language packages) is a core architectural principle of the product. Self-contained modules of discrete code are organized by feature, thereby reducing each module’s external dependencies.

If a module is self-contained, then you can modify or replace it without affecting other areas of the code. This loose coupling of software components reduces the ripple effects throughout your code base of changing code.

See the PHP Developer Guide for detailed instructions on how to create modules.

Rich product ecosystem

The wider Magento ecosystem provides an extensive community and rich third-party marketplace for extensions. Visit Commerce Marketplace for an overview of the many modules and themes available for download and to buy modules and theme packages, which offer more possibilities for extending your storefront.

Open-source software to create and manage extensions

Magento is built on open-source technologies, created for the development community. For example, it uses Composer to manage dependencies. See Technology Stack for a complete list of technologies used.

Coding standards

Adherence to standard best practices for PHP and JavaScript code ensures that the code base is sound. Magento has adopted most of the PSR2 Coding Standards for PHP. See Coding Standards for more information.

Upgrade and versioning strategies

Magento has well-defined upgrade and versioning strategies that can help you avoid any problems with software component dependencies. Add modules after confirming that the module version is compatible with the Magento Framework version.

Web APIs

Magento or third-party services can be configured as a web API (REST or SOAP) with some simple XML. You can use these services to integrate your Magento installation into third-party applications, such as CRM (Customer Relationship Management), ERP (Enterprise Resource Planning) back office systems, and CMS (Content Management Systems).

See Getting Started with Magento Web APIs for more information.

Flexible attribute types

You can enhance your storefront by adding unique attributes to the default product attributes. For example, you might need to add a new attribute to describe a product, such as texture or an industry-specific rating. You can add these attributes from the Admin, and the storefront displays them.

Attribute type Displayed by storefront?
EAV no
Custom yes
Extension no

Attribute types fall into three general categories:

  • EAV (Entity-Attribute-Value) attributes are site-specific attributes that you can define for a local site using the Admin.

  • Custom attributes are a subset of EAV attributes. Objects that use EAV attributes typically store values in several MySQL tables. The Customer and Catalog modules use EAV attributes.

  • Extension attributes often use more complex data types than custom attributes. These attributes do not appear in the storefront. Extension attributes are introduced by modules.

See PHP Developer Guide for information about using attributes.

Service contracts, dependency injection, and dependency inversion

Service contracts provide a new way to access public API endpoints. These PHP interfaces offer robust, stable extension points to which clients can connect. Service contracts define the endpoints that function as a module’s public API. Defining these endpoints is an essential part of adding a module.

Service contracts are discussed throughout the Magento documentation set. See Service layer for a high-level introduction. See PHP Developer Guide for a more detailed discussion of service contracts and dependency injection.

Magento implements dependency injection along with service contracts. Dependency injection provides a mechanism for changing a module’s behavior without altering the client or understanding nitty-gritty details of implementation. Both dependency injection and its related concept dependency inversion support Magento’s fundamental architectural principles of modularity and ease-of-extensibility. They strongly encourage basic coding practices that support the loose coupling of software modules.

See PHP Developer Guide for information on both dependency injection and service contracts.


Plug-ins, like modules, are a mechanism for adding features to the core Magento product. Plug-ins enable you to make changes to the behavior of any public method in a Magento class. You can consider it a form of extension that uses the Plugin class.

Plug-ins are also called interceptors. Applications use the plug-in pattern to change method behavior without modifying the actual class. Plug-ins can typically intercept method processing before or after the method runs, or only when the method throws an exception.

See Plug-ins in PHP Developer Guide for information on declaring and prioritizing plug-ins.

Related topics

Architectural basics

Global features that support extensibility

Ease of frontend customization

Extensibility and modularity