/**
* Add a set of tables to the internal array
- * @param mixed $tables Table name or array of table names
- * @param mixed $alias Table alias, or null for no alias. Cannot be
+ * @param string|string[] $tables Table name or array of table names
+ * @param string|null $alias Table alias, or null for no alias. Cannot be
* used with multiple tables
*/
protected function addTables( $tables, $alias = null ) {