Hook Registry
Hook_Registry (util/class-hook-registry.php) is a static wrapper around add_action() and add_filter() that refuses duplicate registrations. It exists because the example controllers can be instantiated more than once in a request — on a settings page, in a metabox, and during a wizard step — and WordPress would happily attach the same callback several times.
Usage
use My_Plugin\Util\Hook_Registry;
Hook_Registry::add_action( 'admin_enqueue_scripts', array( $this, 'enqueue' ) );
Hook_Registry::add_filter( 'the_content', array( $this, 'append_widget' ), 20 );
Both return true when the hook was registered and false when it was rejected as a duplicate — or as invalid.
Methods
| Method | Purpose |
|---|---|
register( $hook_type, $hook_name, $callback, $priority = 10, $args = 1 ) |
The underlying registration. $hook_type is action or filter. |
add_action( $hook_name, $callback, $priority = 10, $args = 1 ) |
Shorthand for register( 'action', … ). |
add_filter( $hook_name, $callback, $priority = 10, $args = 1 ) |
Shorthand for register( 'filter', … ). |
remove( $hook_type, $hook_name, $callback, $priority = 10 ) |
Unregisters and forgets a hook. |
remove_action() / remove_filter() |
Type-specific shorthands. |
get_hooks() |
The full registry: type, name, callback, priority, argument count, and closure ID. |
remove_all_hooks() |
Unregisters everything the registry knows about. |
create_hook_key() / callback_to_string() |
Build the identity key used for deduplication. |
What counts as a duplicate
The identity key combines the hook name, a string representation of the callback, and the priority. Functions, static and instance method arrays, and invokable objects all resolve to a stable string, so registering the same callback twice at the same priority is caught. The same callback at a different priority is a distinct hook and registers normally.
Closures are the exception: each closure gets a fresh uniqid(), so two identical-looking closures are always treated as different callbacks. If you need deduplication, pass a named function or a method array instead.
Invalid input
register() returns false without touching WordPress when the hook type is neither action nor filter, the hook name is empty, the priority is negative, or the argument count is below one.