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Category: Symfony Framework

In the Symfony Framework, a listener is a class that listens to a specific event and executes a specific code when that event occurs. Listeners are used extensively in Symfony to implement various functionalities in a decoupled and reusable way.

Listeners are part of Symfony's event-driven architecture, where events are dispatched and listeners are registered to handle those events. When an event is dispatched, all registered listeners for that event are called in the order of their priority (which can be set when registering the listener), and each listener can execute its own code to respond to the event.

Listeners can be implemented in different ways in Symfony, depending on the context and the use case. Some examples of listeners in Symfony include:

- Kernel event listeners: These listeners are used to handle events related to the Symfony kernel, such as the request, response, exception, and termination events. Kernel event listeners can be used to modify the behavior of the Symfony kernel, add custom functionality to the application, or handle errors and exceptions in a centralized way.


- Doctrine event listeners: These listeners are used to handle events related to Doctrine, such as the prePersist, postPersist, preUpdate, postUpdate, preRemove, and postRemove events. Doctrine event listeners can be used to execute custom code before or after a specific Doctrine operation, validate or transform data, or implement custom business logic.


- Form event listeners: These listeners are used to handle events related to Symfony forms, such as the preSubmit, postSubmit, preSetData, and postSetData events. Form event listeners can be used to modify the form data, validate the form input, or execute custom code before or after the form submission.


Overall, listeners are a powerful and flexible mechanism in Symfony that enable developers to implement complex functionalities in a modular and extensible way.

Further reading:

Sample Listener implementation in Symfony 5+

Symfony Events and Listeners.

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Category: Distributed Systems within an Organization

Microservices is a particular variant of Service Oriented Architecture Pattern. A System is broken down into a set of micro applications, each one independent of the other and communicating each one to other by REST, gRPC, Sockets, etc.

An application can be considered a Microservice if it only works with one Entity, lets say Vendors Service, that handles Create, Update and Delete Vendors, or if it only handles one process, lets say an Email Service, that handles sending emails. Other important characteristic is that a Microservice has it own micro DB Server. Docker and Kubernetes are the most common environments to implement this Pattern.

A typical PHP REST Microservice has these 3 docker containers:

  • Nginx Web Server Container
  • PHP Container
  • DB Server Container

When working locally, we use docker compose for container orchestration and each Microservice's Nginx container listening in a different port. When working on the cloud, we use Kubernetes as container orchestrator and a Ingress Controller that will take care of sending the request to the appropriate Microservice. In the cloud, these 3 containers are organized in a Pod.

 

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Category: Symfony Framework

Caching is an important concept in web development that helps to improve the performance of web applications. Symfony 5+ provides various caching mechanisms that you can use to improve the performance of your application, mostly for requests that will require lot of processing. This helps in reducing response times ,but a the same time in reducing system resources usage, allowing the System to be able to serve many more client requests. A good caching strategy is crucial for improving Application performance and reducing costs in infrastructure.

Prerequisites:

 

 Step 1. Install Symfony Cache component.