$status = $db->register('/path/to/my_udf.lua', 'my_udf');
$key = $db->initKey('test', 'demo', 'foo');
$db->apply($key, "sample", "list_append", ["things", "!!!"]);
$status = $db->scanApply("test", "users", "rec_udf", "accumulate", ["balance", "income"], $scan_id);
$where = Aerospike::predicateBetween("age", 20, 29);
$status = $db->aggregate("test", "users", $where, "mymod", "group_count", ["first_name"], $names);
user definied functions