Fatal error: Class 'think\Exception' not found in D:\wwwroot\www.9kzb.com\thinkphp\library\think\exception\ErrorException.php on line 22

Fatal error: Uncaught Error: Class 'think\exception\ErrorException' not found in D:\wwwroot\www.9kzb.com\thinkphp\library\think\Error.php:87 Stack trace: #0 [internal function]: think\Error::appShutdown() #1 {main} thrown in D:\wwwroot\www.9kzb.com\thinkphp\library\think\Error.php on line 87