A function used to pull all of the expired events ids from EE.

example_function.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

if ( class_exists( 'EE_Registry' ) ) {
		$exclude_query[0] = array( 'Datetime.DTT_EVT_end' => array( '>', EEM_Datetime::instance()->current_time_for_query( 'DTT_EVT_end' ) ) );
		//first get all events that have datetimes where its not expired.
		$exclude_event_ids =  EE_Registry::instance()->load_model( 'Event' )->get_all_wpdb_results( $exclude_query, OBJECT_K, 'Event_CPT.ID' );
		$exclude_event_ids = array_keys( $exclude_event_ids );

		//Grab all events where the Datetime end date is less than today (expired) excluding the events we pulled in above.
		$where_params['AND'] = array(
				'Datetime.DTT_EVT_end' => array( '<', EEM_Datetime::instance()->current_time_for_query( 'DTT_EVT_end' ) ),
				'EVT_ID' =>  array( 'NOT IN', $exclude_event_ids )
				);
		
		$query_params[0] = $where_params;
		
		$expired_event_ids =  EE_Registry::instance()->load_model( 'Event' )->get_all_wpdb_results( $query_params, OBJECT_K, 'Event_CPT.ID' );
		$expired_event_ids = array_keys( $expired_event_ids );

		//$expired_event_ids is now an array containing the ID's of the expired events.

		//If using Kint debugger you can view this using:
		//d($expired_event_ids);
		
		//Otherwise just:
		//var_dump($expired_event_ids)
}