smarty为什么说调用未知的方法“register_function”

Question

Fatal error: Uncaught exception 'SmartyException' with message 'Call of unknown method 'register_function'.' in C:\wamp\www\19\system\libs\sysplugins\smarty_internal_templatebase.php:806 Stack trace: #0 [internal function]: Smarty_Internal_TemplateBase->__call('register_functi...', Array) #1 C:\wamp\www\19\system\system.inc.php(22): SmartyProject->register_function('unhtml', 'unhtml') #2 C:\wamp\www\19\index.php(4): require('C:\wamp\www\19\...') #3 {main} thrown inC:\wamp\www\19\system\libs\sysplugins\smarty_internal_templatebase.php on line 806