To what types of events can key handlers be attached?

In PHP, key event handlers can be attached to various types of events depending on the architecture and framework used. The main types of events to which handlers are often attached:

• HTTP request events — for example, handling incoming requests, routing.
• Application lifecycle events — initialization, shutdown.
• Database events — creation, updating, deletion of records (e.g., in ORM).
• Custom events — events defined by the developer for specific logic.
• Session and authentication events — user login, logout, session update.

For example, in the Laravel framework, handlers can be attached to model events:

User::created(function ($user) {
    // Code executed after a user is created
});

Thus, key event handlers can be attached to system and custom events, ensuring application reactivity and extensibility.