function my_event_handler($event) { // Retrieve the first argument from the event $arg1 = $event->get_arg(0); // Do something with the argument if ($arg1 === 'foo') { // Handle the event } else { // Handle a different event } } // Define an event with two arguments $event = new WP_Event('my_event', array('foo', 'bar')); // Trigger the event and pass it to the event handler do_action('my_event', $event);In this example, the `get_arg` function is used to retrieve the first argument from an event. The argument is then used to determine how to handle the event. The package/library that this code snippet is using is WordPress, specifically the `WP_Event` and `do_action` functions. However, the `get_arg` function is a general PHP function and can be used in other contexts as well.