Execution time

Hey, @islp! Good question.

Since the hook is part of the plugin, you can use it after the plugin has been initialized. This means you need to ensure your calls are executed after the plugins_loaded hook is triggered.

Got it. That is exactly what WP hooks were created for.

When you definitely call it before plugins_loaded fired, you have to hook on it

add_action( 'plugins_loaded', function() { 
  do_action( 'logger' );
} );

But if you arn’t sure whether your call runs before or after it, you could add an extra check

$do_log = function () {
  do_action( 'logger' );
};

// Check if the action 'plugins_loaded' has not been fired,
// then perform logging on this action.
if ( ! did_action( 'plugins_loaded' ) ) {
	add_action( 'plugins_loaded', $do_log );
} else {
	$do_log();
}

Another option is to turn this Logger into a “must use” plugin. That way, its API becomes available before any regular plugins are loaded.