Magento 2 Modules

A Magento 2 module is a self-contained package of code that extends or modifies Magento's functionality. Every feature in Magento is implemented as a module - from catalog management to checkout to payment processing.

Module components:

• registration.php - Registers the module with Magento's ComponentRegistrar
• module.xml - Declares module name, version, and dependencies
• etc/ - Configuration files (di.xml, routes.xml, events.xml, etc.)
• Api/ - Service contract interfaces
• Model/ - Business logic and data models
• Controller/ - Request handlers
• Block/ - View layer logic
• view/ - Templates, layouts, CSS, JavaScript
• Setup/ - Database schema and data install/upgrade scripts

Minimum module structure:

app/code/Vendor/Module/
├── registration.php
└── etc/
    └── module.xml

registration.php:

<?php
use Magento\Framework\Component\ComponentRegistrar;

ComponentRegistrar::register(
    ComponentRegistrar::MODULE,
    'Vendor_Module',
    __DIR__
);

module.xml:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="Vendor_Module" setup_version="1.0.0">
        <sequence>
            <module name="Magento_Catalog"/>
        </sequence>
    </module>
</config>

Magento 2 modules go through several lifecycle stages, each managed by specific commands and configuration.

1. Development Phase:

• Create module directory and registration.php
• Define module.xml with dependencies
• Implement module functionality
• Run setup:upgrade to install/upgrade schema

2. Installation:

# Enable module
php bin/magento module:enable Vendor_Module

# Run upgrades and compile
php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento cache:clean

3. Disabling:

# Disable module (keeps code, removes config)
php bin/magento module:disable Vendor_Module

# Remove module completely
php bin/magento module:uninstall Vendor_Module

4. Uninstallation:

# Full uninstall (deletes code, database, config)
php bin/magento module:uninstall --clear-static-content Vendor_Module

Module states:

• enable - Module is active and loaded
• disable - Module code exists but is not loaded
• uninstall - Module is removed from the system

Check module status:

php bin/magento module:status
php bin/magento module:status Vendor_Module

View enabled modules in app/etc/config.php - this file contains the master list of all enabled modules.

Module dependencies in Magento 2 ensure proper load order and prevent conflicts between modules.

Dependency types:

1. Hard dependencies - Module cannot function without the dependency

<module name="Vendor_Module" setup_version="1.0.0">
    <sequence>
        <module name="Magento_Catalog"/>
        <module name="Magento_Customer"/>
    </sequence>
</module>

2. Soft dependencies - Module works better with the dependency but can function without it

<module name="Vendor_Module" setup_version="1.0.0">
    <sequence/>
    <suggest>
        <module name="Magento_Inventory"/>
    </suggest>
</module>

Dependency rules:

• Circular dependencies are not allowed
• Dependencies are loaded in sequence order
• Module version numbers track schema changes
• setup:upgrade applies pending upgrades in dependency order

Resolve dependency conflicts:

# Check for dependency issues
php bin/magento setup:di:compile 2>&1 | grep -i dependency

# View module sequence
php bin/magento module:status --version

Module version management:

<!-- Module version upgrades -->
<module name="Vendor_Module" setup_version="2.0.0">
    <sequence>
        <module name="Magento_Catalog" setup_version="2.4.0"/>
    </sequence>
</module>

When setup_version increases, Magento runs the corresponding UpgradeSchema and UpgradeData scripts in the module's Setup/ directory.

Magento discovers modules through the ComponentRegistrar system and maintains a module list in configuration.

Module discovery process:

1. Magento scans app/code/ and vendor/ directories
2. Looks for registration.php files
3. Calls ComponentRegistrar::register() for each module
4. Builds module list from app/etc/config.php
5. Loads enabled modules in dependency order

Registration with area codes:

<?php
// app/code/Vendor/Module/registration.php
use Magento\Framework\Component\ComponentRegistrar;

ComponentRegistrar::register(
    ComponentRegistrar::MODULE,
    'Vendor_Module',
    __DIR__
);

Module list in config.php:

// app/etc/config.php (excerpt)
return [
    'modules' => [
        'Magento_Catalog' => 1,        // 1 = enabled
        'Magento_Customer' => 1,
        'Vendor_Module' => 1,
        'Magento_SomeDisabledModule' => 0,  // 0 = disabled
    ]
];

Listing all modules:

# Show enabled modules
php bin/magento module:status

# Show specific module status
php bin/magento module:status Vendor_Module

# Show modules with versions
php bin/magento module:status --version

Force module refresh:

# Rebuild module list
php bin/magento setup:upgrade --force

# Clear module configuration cache
php bin/magento cache:clean config