As you have heard, Magento 2 is using the events driven architecture which will help too much to extend the Magento functionality. We can understand this event as a kind of flag that rises when a specific situation happens. .

Dispatch event

In Magento 2 Events List, we can use the class Magento\Framework\Event\Manager to dispatch event. For example, we create a controller action in PHPCodez_First to show the word “Hello World” on the screen:

File: app/code/PHPCodez/First/Controller/Index/Second.php

<?php
namespace PHPCodez\First\Controller\Index;

class Second extends \Magento\Framework\App\Action\Action
{

public function execute()
 {
 echo "PHPCodez - Your Second Module Is Ready. Cheers !!!";
 exit;
 }
}

Now we want to dispatch an magento 2 event list which allow other module can change the word displayed. We will change the controller like this:

File: app/code/PHPCodez/First/Controller/Index/Second.php

<?php

namespace PHPCodez\First\Controller\Index;

class Second extends \Magento\Framework\App\Action\Action
{

public function execute()
 {
 $textDisplay = new \Magento\Framework\DataObject(array('text' => 'PHPCodez'));
 $this->_eventManager->dispatch('phpcodez_first_display_text', ['mp_text' => $textDisplay]);
 echo $textDisplay->getText();
 exit;
 }
}

The dispatch method will receive 2 arguments: an unique event name and an array data. In this example, we add the data object to the event and call it back to display the text.

Catch and handle event

Event area

Magento use area definition to manage the store. We will have a frontend area and admin area. With the configuration file, they can be put in 3 places:

Under etc/ folder is the configuration which can be used in both admin and frontend.
Under etc/frontend folder will be used for frontend area.
Under etc/adminhtml folder will be used for admin area.

The same with the event configuration file. You can create events configuration file for each area like this:

Admin area: app/code/PHPCodez/First/etc/adminhtml/events.xml
Frontend area: app/code/PHPCodez/First/etc/frontend/events.xml
Global area: app/code/PHPCodez/First/etc/events.xml

Create events.xml

In this example, we only catch the event to show the word PHPCodez – Event on the frontend so we should create an events.xml file in etc/frontend folder.

File: app/code/PHPCodez/First/etc/frontend/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
 <event name="mageplaza_helloworld_display_text">
 <observer name="phpcode_display_text" instance="PHPCodez\First\Observer\ModifyText" />
 </event>
</config>

In this file, under config element, we define an event element with the name is the event name which was dispatch above. The class which will execute this event will be define in the observer element by instance attribute. The name of observer is used to identify this with other observers of this event.

With this events.xml file, Magento will execute class PHPCodez\First\Observer\ModifyText whenever the dispatch method of this event was called on frontend area. Please note that, we place events.xml in the frontend area, so if you dispatch that event in the admin area (like admin controller), it will not run.

Observer

Now we will create a class to execute above event.

File: app/code/PHPCodez/First/Observer/ModifyText.php

<?php

namespace PHPCodez\First\Observer;

class ModifyText implements \Magento\Framework\Event\ObserverInterface
{
 public function execute(\Magento\Framework\Event\Observer $observer)
 {
 $displayText = $observer->getData('mp_text');
 echo $displayText->getText() . " - Event </br>";
 $displayText->setText('Execute event successfully.');

return $this;
 }
}

This class will implement the ObserverInterface and declare the execute method. You can see this simple method to know how it work.

Clean the cache using the below commnd and reload the page

php bin/magento cache:clean