Call to undefined function mb_internal_encoding 问题

Laravel框架错误提示：

[Sat May 16 11:34:36.283788 2015] [:error] [pid 9540:tid 828] [client 127.0.0.1:62578] PHP Fatal error: Call to undefined function Illuminate\\Foundation\\Bootstrap\\mb_internal_encoding() in E:\\PHPTOOLS\\Apache24\\htdocs\\HParent\\vendor\\laravel\\framework\\src\\Illuminate\\Foundation\\Bootstrap\\LoadConfiguration.php on line 43

Call to undefined function mb_internal_encoding() in 错误，