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Listeners and subscribers can be used in the same application indistinctly. The decision to use either of them is usually a matter of personal taste. However, there are some minor advantages for each of them:
- Subscribers are easier to reuse because the knowledge of the events is kept in the class rather than in the service definition. This is the reason why Symfony uses subscribers internally;
- Listeners are more flexible because bundles can enable or disable each of them conditionally depending on some configuration value.
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To avoid having a configuration file that describes which events a listener wants to listen to, create a subscriber.
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A subscriber is a listener with a static
getSubscribedEvents()method that returns its configuration. This allows subscribers to be registered in the Symfony dispatcher automatically.