Magento Plugin Guide: What Is a Magento Plugin & How to Use It

What is a Magento Plugin?

A Magento plugin is a class that allows you to modify or extend the behavior of public methods in existing classes without altering core code. This uses Magento’s Interceptor Design Pattern, enabling safe and upgrade-friendly customization.

Plugins allow you to hook into a method call before, after, or around it, giving you control over input, output, or method logic itself.

Example: Imagine a traffic light controlling cars at an intersection. The traffic light follows a fixed sequence: green, yellow, red. Now, suppose you want to add a pedestrian crossing button that pauses the green light when pressed, letting people cross safely—without rebuilding or replacing the whole traffic system.

Magento plugins work like that pedestrian button: they let you insert extra steps before, after, or around existing actions in Magento’s system, customizing behavior without changing the original setup.

When Should You Use a Plugin?

• To change the behavior of a public method.
• To extend core functionality without overriding full classes.
• To avoid conflicts seen with preferences or rewrites.

Avoid using plugins when:

• You need to target non-public methods.
• The same logic can be done using event observers.
• Performance is critical, as plugins add overhead.

Types of Plugin Methods

1. Before Method – Runs before the target method. Can change arguments.
2. After Method – Runs after the method. Can change return value.
3. Around Method – Wraps the method. Can override or skip it completely.

Step 1: Declare the Plugin in di.xml

<type name="Magento\Customer\Model\Customer">
    <plugin name="custom_plugin" type="Vendor\Module\Plugin\CustomerPlugin" sortOrder="1" />
</type>

Step 2: Create the Plugin Class

<?php

namespace Vendor\Module\Plugin;

class CustomerPlugin
{
    public function beforeSetFirstname(\Magento\Customer\Model\Customer $subject, $firstname)
    {
        $firstname = ucfirst(strtolower($firstname));
        return [$firstname];
    }

    public function afterGetFirstname(\Magento\Customer\Model\Customer $subject, $result)
    {
        return strtoupper($result);
    }

    public function aroundSave(\Magento\Customer\Model\Customer $subject, \Closure $proceed)
    {
        // Custom logic before save
        $result = $proceed();
        // Custom logic after save
        return $result;
    }
}

Best Practices for Using Plugins

• Use only when needed: Excess plugins affect performance.
• No circular dependency: Avoid chaining preferences and plugins on same class.
• Target concrete classes: Don’t use interfaces/abstract classes.
• Test edge cases: Plugins affect base logic—test thoroughly.

Conclusion

Magento plugins let you customize behavior in a precise and maintainable way. When used wisely, they offer flexibility without core code changes. But overuse or misuse can lead to performance issues and unexpected results.