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Magento 2 Fundamentals Of Development

Magento 2 Fundamentals of Development#

Six goals of Magento 2#

  • Streamline the customisation process
  • Update the technology stack
  • Improve performance and scalability
  • Reduce upgrade efforts and costs
  • Simplify Integrations
  • Provide high quality, tested code and resting resources

Greater independence of modules (standalone)


Load only required config files

adminhtml, frontend, crontab, REST web api, SOAL web api, Install

entry point for adminhtml and frontend is index.php

Exceptions 1. Framework files not technically modular and some static files belong to a theme, not a module. 2. Themes include all types of static assets connected to the magento rendering system. Some assets are in the module folder and some are in the theme folder. PHP code is mostly located in modules. 3. Layout files are xml define which elements should be on a page. Blocks are special PHP classes that are usually connected to a template. A block class generates HTML using its template. 4. Each module has its own configuration files: events.xml, routes.xml, acl.xml…Magento merges all these files together. 5. Dependency injection / object instantiation magic is a magento 2 feature. A new object is declared in the constructor, magento will deliver the instance. 6. Naming conventions: routes need a special corresponding controller (and route in route.xml). Layouts are also connected to route names. 7. Events: fired in core, developers can add observers to that event. Plugin: add specific behaviour to every public method of each class.


Config: app/etc: global config db credentials, enabled modules. Not module configuration. Framwork: lib/internal/Magento/Framwork: low level code for logging, db interation, url processing Modules: app/code/magento: Magento business logic and features CLI tool: bin/magento: tool to clear cache etc. Themes: app/design: defines how pages look Dev tools: dev: tools that assist the developer like testing framework

  • Modules

    composer install - `vendor/magento/module-*`
    cloned repo - `app/code/Magento/*`
  • Framework

  • Themes


Magento 2 can be installed by composer install or cloning the repo

File Types#

Configuration files PHP classes Layout instructions (*.xml) Templates (*.phtml) Javascript modules (.js) Javascript templates (*.html) Static assets (css, images)

Config files#

custom config is inside modules etc folder - defines module behaviour global, module and theme

PHP classes#

  • Model/resource and module/collection: interact with db, magento 2 moving away towards api
  • API interfaces: CRUD for modules entities,
  • controllers: handle pages in accordance with MVC
  • Blocks: special classes representing part of a page. Usually connected to a .phtml template file
  • observers: Events fire during different places along its execution flow.
  • plugins:wrapper around any public method of any class
  • helpers: auxillary classes with useful functions
  • setup/upgrade scripts: upgrade the db schema or add data
  • UI components: Allows developer to create a component, an independent element on a page with its own backend part

Dev Process#

Class is placed somewhere along the execution flow, where some method gets executed.

  • Adding class into class’s constructor
  • Creating a plugin
  • Creating an observer

Enabling custom code#

  • Create and register a module
  • Run bin/magneto setup upgrade to executre setup/ugprade scripts
  • modify core classes by creating a plugin
  • Create observers
  • Add your class to the core’s class array in constructor
  • Controllers
  • System configuration


Module is package of code encapsulating a particular busines feture or set of features

Magento 2 module is now in a single folder

Modules are organised per functionality and are smaller

Each module is independent

Located in:

  • app/code/<vendor>/<module_name>
  • vendor/<vendor-composer-namespace>/<modue-name>

Modules in vendor are regsitered with a composer autoload callback:

\Magento\Framework\Module\Registrar::registerModule('<module name', __DIR__)

Eg. Customer module is found app/code/Magento/Customer

Vendor and Module must start with an uppercase character

Code base: /app/code/<Vendor>/<Module> Custom theme files: /app/design/<area>/><Vendor>/<theme>/<Vendor_Module> Custom theme files: /app/design/<Module>/<theme>

Registering a module#
  • custom written modules are in app/code regardless of installation type
  • Grouped by vendors
  • composer installed core modules are in vendor/magneto/module-*
  • Every module must have a etc/module.xml and a registration.php

Includes name, version and dependencies

it is located in modules etc folder. Other folders usually start with a capital letter.

<?xml version="1.0"?>
<config xmlns:xsi="" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
        <module name="Vendor_ComponentName" setup_version="2.0.0"/>

More info on module.xml


Instructions on how to find a module

ComponentRegistrar::register(ComponentRegistrar::MODULE, '<VendorName_ModuleName>', __DIR__);

More info on registation.php

Module dependencies#

  • multiple modules can’t be responsible for 1 feature
  • One module cannot be responsible for multiple features
  • modules explicitly declare dependencies
  • theme dependencies must be declared
  • disabling or removing a module does not remove others

Modules can be dependent on:

  • Other modules
  • PHP extensions
  • Libraries

Soft order dependencies are declared in module.xml other dependencies are in composer.json

Hard dependency: can’t function without module

  • uses code: instances, class constants, static methods, pubic class properties, interfaces and traits
  • strings from another module
  • deserialises object from another module
  • uses or modifies datbase tables used by another module

Soft dependency: can function without

  • directly checks another module’s availability
  • extends another modules configuration
  • entends another modules Layout
Declaring module dependency#
  • Name and declare module (module.xml)
  • Delcare dependencies in composer.json
  • Define desired load order (module.xml) with sequence element- optional

File System#

  • app - core code (cloned repo), custom modules, themes, global config
  • bin - cli tool
  • dev - tools for developers
  • lib - external libraries not available in composer
  • vendor - composer folder
  • pub - public folder. /static folder for files
  • setup - installation specific files
  • var - cache, generated code, logs and other files (uploaded csv)
App Folder#
  • app/etc - global configuration
  • app/code - custom modules (cloned repo - core modules)
  • app/design - themes
  • app/i18n - translations
  • app/Bootstrap.php, app/autoload.php, app/functions.php important…begin execution process
File System#
  • app/code/Magento/ - Core
  • lib/internal/Magento/Framework - Framework
Module Folder#

The only required folder is etc

  • Api
  • Block
  • Console
  • Controller
  • etc
  • Helper
  • i18n
  • Model
  • Observer
  • Plugin
  • Registration.php
  • Setup - upgrade scripts
  • Test
  • Ui
  • view - layout xml, templates, static view files
View subfolder#
  • frontend - templates, layout, web (images, js, widegets.css, zoom.css)
  • adminhtml
  • base

Typical module file structure

  • Static files placed in theme rather than specific module when it is a general file affecting all pages.


Development mode#
  • static file materialisation not enabled
  • uncaught exceptions displayed in browser
  • exceptions thrown in wrror handler, not logged
  • Logging in var/report highly detailed
Production mode#
  • Best performance
  • Exeptions only written to log
  • Disabled static file materialisation
Default mode#
  • Used when no mode specified
  • Hides exceptions and writes to log files
  • static file materialisation is enabled
  • Not recommened for production, caching impacts performance negatively
Maintenance mode#
  • make site unavailable
  • Set flag var/.maintenance.flag
  • Can specifify people with access var/.maintenance.ip
Setting mode#
  • Use nginx environment variable
Command line tool#
  • Enable and disable: magento module:enable <module-list>
  • Change caching app/etc/env.php
  • Cleaning cache: from admin,using cli, manually removing cache files

DI and Object Manager#

Dependency Injection - Manage object dependencies by settings objects in current objects constructor The object manager is responsible for creating the objects a class requires.

Lots of depedency limits code reuse and makes moving components to new projects difficult

Dependency injection is configuration that is XML-based and validated by XSD

Eg. You need a storeManager instance in the Product class. You can declare an argument with type StoreManagerInterface in the constructor of the product. Then using di.xml you have to define which class will be substituted for the interface.

Constructor has a list of objects assigned to protected properties, then used inside a class.

Class Instantiation#

di.xml specifies the List or interfaces, classes and factories sent into __construct() method

The best candidate to use di is a singleton-type class - only single instance but used in multiple places. Eg. Cache, session, registry, helpers. Factory / API classes als match this definition.

Not every class has to be injected. Eg. an entity class like product depends on data from database. So a factory is recommended for injecting.


public function __construct(\Magento\Catalog\Model\ProductFactory $factory) {
  $this->factory = $factory;


public function someFunction(){
  $product = $this->factory->create();

The factor class may not exist, when the DI mechanism identifies a class ending in Factory and it does not exist it generates it in var/generation

Object Manager#

A class that:

  • Creates objects
  • Implements singleton pattern
  • Manages dependencies
  • Automatically instatiates parameters

Parameters - variables declared in the constructor signature arguments - values passed to the constructor when the class instance is created

Has replaced the Mage class.

Magento 1 instantiation was centralised most classes created through Mage class and a config file. 4 Generic patterns:

  • Abstract Factory
  • Factory Method
  • Singleton
  • Builder

For all singletons the registry was used, so you could request singletons from the registry, creating them if not present.

Magento 2#

Object Manager has 2 methods: get and create. Get method: return a singleton object called Shared Instance from protected registry. Create method: creates a new instance of a given class

Mage was a static class always included in the beginning of the request flow. Now the object manager is no longer static or globally available.

Best practice to avoid calling the object manager directly.

Object Manager Usage#

To use the ObjectManager include it in the constructor (__construct())

Then assign it to the protected property and use it in your class:

$this->objectManager = $objectManager

$objectManager->get(’Magento\Catalog\Api\ProductRepositoryInterface’); will return the same implementation of… ProductRepositoryInterface as you would receive by including it in the constructor

You should not use ObjectManager in your code as it breaks the DI concept

Autogenerated Classes#

factory classes, Interceptors and proxies are autogenerated.

Interceptor: class that allows plugin functionality to work. When you require a class that has a registered plugin, magento generates an interceptor with the same method as the required class but will call a plugin in that method.

Interceptors use PHP traits to extend both the abstract interceptor and the original class.

Proxy - tool that helps with circular dependencies, and relates to an internal implementation of how DI works. So you won’t have to deal with them directly.

Object Manager Configuration#

Uses config from di.xml to define which instance to deliver into the constructor of a class

Each module can have multiple di.xml files - global or specific

  • You need to use the real class name including the PHP namespace when you require an instance of a class
  • Creation of objects is managed for you
  • Recursively creates any arguments for the objects yourboject requires
  • Declaring an interface in the constructor, the boject manager automatically creates the matching implementation for it.
  • Thinking in terms of interfaces and not implementations
Where to specify object manager configurations#
  • Global across all of magento: app/etc/di.xml
  • Entire module <your directory>/etc/di.xml
  • Area specific configuration: <your directory>/etc/<area>/di.xml

Magento only uses 1 di.xml…the merged one

Defining preferences#
  • Preferences can be defined for interfaces and regular classes
  • Preferences define which classes will be instantiated for a constructor argument of your class

Best Practice to request only interfaes and not concrete classes.

Eg. Request \Magneto\Framework\App\Response\HttpInterface instead of \Magento\Framework\App\Response\Http

Defining Arguments#

There are different types of arguments: string, array, object DI defines which objects should be used as an argument when a new instance is created

Sometimes you need a specific product but the object manager can only deliver a generic product. It can’t provide a loaded entity. As a result this object type is not injectable.

Some objects have to be gotten with the object manager

DI affecting parameters of a class#
  1. Define which classes correspond to certain interfaces. An interface cannot be instantiated, a class implements the interface. Using DI we can figure out exactly which class is being used. Look at \Magento\Catalog\etc\di.xml search for ProductAttributeRepositoryInterface, a line substitutes Magento\Catalog\Model\Product\Attribute\Repository assigned to parameter $metadataService

  2. Define a specific parameter for a specific class. Define a specific instance for a specific class. For products you may need a particular class only for products. Eg. magento data parameter. With di.xml we can add something to data parameter. So for \Magento\Catalog\Model\Product\ReservedAttributeList.php look at parameters of constructor and see $productModel. Now search productModel in Magento/Catalog/etc/di.xml

Example: So when instance of this class is created, productModel is set to the string \Magento\Catalog\Model\Product

<type name="Magento\Catalog\Model\Product\ReservedAttributeList">
        <argument name="productModel" xsi:type="string">\Magento\Catalog\Model\Product</argument>
        <argument name="reservedAttributes" xsi:type="array">
            <item name="position" xsi:type="string">position</item>
        <argument name="allowedAttributes" xsi:type="array">
            <item name="type_id" xsi:type="string">type_id</item>
            <item name="calculated_final_price" xsi:type="string">calculated_final_price</item>
            <item name="request_path" xsi:type="string">request_path</item>
Configuration Shared Argument#
  • shared object == singleton
  • Use same instance of a class within several other classes

In di.xml if the node has shared="false" it won’t be shared.

  • Can use on both type and argument nodes with the xsi:type="object"


  • Plugins extend / change the behaviour of a native method within a magento class
  • Plugins change behaviour of original class, but not class itself
  • Can’t use with final methods, final classes, private methods or classes without dependency injection.

plugins allow you to modify a single method, preference allows you to change a whole class.

  • Events: commonly handle external actions or input
  • Plugins: Allow you to customise a method. Executed sequentially.

Magento 1 used events and rewrites. Sometimes events not in correct places and too many events might cause many firing hurting response time. Class rewrites need a thorough understanding.

Declaring a plugin#

Use di.xml:

  <type name="{ObservedType}">
    <plugin name="{pluginName}"


  • type name: class, inheritance or virtual type the plugin observes
  • plugin name: name identifying the plugin
  • plugin type: name of plugin class or virtual type. Naming convention: <ModelName>\Plugin


  • plugin sort order: order that plugins calling the same method run
  • plugin disabled: true to disable

The syntax is very simple. The way it works: you define a plugin – you create a class within another class, then inside that class you can define which methods write the plugin. - MagentoU

  • Before-Listener: Chnage an argument before a method is called

    public function beforeSetName(\Magento\Catalog\Model\Product $subject, $name){ return [‘(‘ . $name . ‘)’]; }

  • After-Listenenr: Add after

    public function afterSetName(\Magento\Catalog\Model\Product $subject, $result){ return ‘|’ . $result . ‘|’; }

  • Change arguments and returned values of original method use an aroundlistener

    namespace My\Module\Model\Product;

    class Plugin { public function aroundSave(\Magento\Catalog\Model\Product $subject, \Closure $proceed) { $this->doSmthBeforeProductIsSaved(); $returnValue = $proceed(); if ($returnValue){ $this->postProductToFacebook(); } retunr $returnValue; } }

  • $subject provides access to all public methods of the original class

  • $process is a ambda that will call the next plugin or method

further arguments passed to net plugin with $proceed()

Can also ovveride an original method (a conflicting change)

Sequence of plugins#
  1. before listener in plugin with highest priortiy (smallest sortOrder)
  2. around listener in plugin with highest priorty
  3. Other before listeners
  4. other around listeners
  5. after listneer of plugin with lowest priorty (highest sortOrder)
  6. after listeners in reverse sort order
Configuration inheritance#

We can create a module, make it dependent from the core module, and redefine preference for a certain interface. Similar to a magento 1 rewrite. Compiler tool can minimise the performance impact.


Object manager checks whether the are any plugins registered for any methods of a required class. If so it generates an interceptor class. Interceptor extends the original class but wraps its methods to all plugin to be called before, after or instead. They are creted in var/generation folder


External actions

Event-observer pattern. Objects (subjects) and their list of dependents (observers). Events trigger objects to notify their observers of state changes.

Magento 1 used Mage::dispatchEvent(), magento 2 uses the special event manager class.

declared in events.xml

Eg. Magento\Checkout\Model\OnePage method saveOrder():

      'order' => $order,
      'quote' => $this->getQuote()

Then in Magento/CatalogInventor/etc/events.xml:

<event name="checkout_submit_all_after">
  <observer name="inventory" instance="Magento\CatalogInventory\Observer\CheckoutAllSubmitAfterObserver"/>
Observer class#

Magento\CatalogInventor\Observer\CheckoutSubmitAllAfterObserver and execute() function

public function execute(EventObserver $observer)
  $quote = $observer->getEvent()->getQuote();
  if (!$quote->getinventoryProcessed()){
  return $this;

event object contains event’s parameters

Module Configuration#

Files split into funtion

  • app/etc/config.php - delcaration of all modules
  • app/etc/env.php - db connectino info

  • module.xml - module declaration

  • config.xml - default admin settings
  • events.xml - observers and events they are subscribed to
  • di.xml - dependency injection config
  • routes.xml - lists the routes and routers

Auto completion for xsd

Storing config values#
  • Database: Merchants (core_config_data)
  • ML files: Developers, technical config

Table core_config_data is the same as magento 1.

If scope is website then scope_id is treated as website_id If scope is store then store_id for global scope does not apply

Configuration scopes#
  • Global: config file in etc/
  • Frontend: etc/frontend
  • Admin: etc/adminhtml
Load order of config files#
  • Primary: loaded on bootstrap (config for app start and install specific)
  • Global: All config files common across all app areas
  • Area-specific: Files that apply to specific areas such as adminhtml
Merging Config files#

Merged based on Fully qualified Xpaths Special attribute is defined in $idAttributes array After 2 XML documents are merged, resulting document contains all nodes from the original files Second XML file supplements or overwrites nodes in the first XML file


Each file is validated against a schema

Eg. events.xml is validated against events.xsd

Validated against: lib/internal/Magento/Framework

All config files are processed by Magento\Framework\Config. Loan, merge, validate and convert into array.

Interfaces to manage config files:#
  • \Magento\Framework\Config\DataInterface - config data within a scope
  • \Magento\Framework\Config\ScopeInterface - Identifies current application scope
  • \Magento\Framework\Config\FileResolverInterface - identies files read by \Magento\Framework\Config\ReaderInterface
  • \Magento\Framework\Config\ReaderInterface - reads config from storage
Loading XML configuration#
  • Config: Class that is used to get access to the config values
  • Reader: reads a file
  • SchemaLocator: encapsulates path to the schema
  • Converter: Converts XMl to array
  • XSD: schema file

New config files must be accompanied with an XSD validations schema

Creating a custom config file#


  • XML file
  • XSD schema
  • Config PHP file
  • Config reader
  • Schema locator
  • Converter

Error Reporting#

Magento uses strongest error reporting, even PHP notice will cause an exception