public static function get_all_targets() : array {
        if (self::$alltargets !== null) {
            return self::$alltargets;
        }

        $classes = self::get_analytics_classes('target');

        self::$alltargets = [];
        foreach ($classes as $fullclassname => $classpath) {
            $instance = self::get_target($fullclassname);
            if ($instance) {
                self::$alltargets[$instance->get_id()] = $instance;
            }
        }

        return self::$alltargets;
    }