How to handle exceptions using events in symfony 4?

@aubrey 

In Symfony 4, you can handle exceptions using events by following these steps:

Step 1: Create a new event class

• Create a new class that extends the SymfonyComponentEventDispatcherEvent class.
• Add necessary properties and methods to the class that will hold the information you need to handle the exception.

Step 2: Create a new event listener

• Create a new class that implements the SymfonyComponentEventDispatcherEventSubscriberInterface interface.
• Implement the getSubscribedEvents method and define the list of events you want to listen to.
• Implement the event handling method(s) to handle the exceptions.

Step 3: Dispatch the event

• In the code where you want to handle an exception, dispatch the event by using the SymfonyComponentEventDispatcherEventDispatcherInterface service.
• Pass an instance of your event class as an argument to the dispatch method.

Step 4: Handle the exception in the event listener

• In your event listener class, implement the event handling method(s) that were defined in the getSubscribedEvents method.
• Inside the event handling method, you can access the exception information and handle it accordingly.

Step 5: Register the event listener as a service

• Register your event listener class as a service in your Symfony configuration files (e.g., services.yaml or services.xml).
• Make sure to give your event listener service a unique name.

That's it! You have now implemented exception handling using events in Symfony 4. Whenever the specified event is dispatched, your event listener will be triggered and it can handle the exception accordingly.