Err: Controller 'mainController' is not exists!

75.  $action_name = 'action'.$__action;
 76. 
77.  if(!method_exists($controller_name, $action_name)) {
 78.      if(!method_exists('BaseController', 'err404')){
 79.          if(!class_exists($controller_name, true)) {
80.              err("Err: Controller '$controller_name' is not exists!");
81.          }else{
 82.              err("Err: Method '$action_name' of '$controller_name' is not exists!");
 83.          }
 84.      }else{
 85.          BaseController::err404($__module,$__controller, $__action);
1.  2.  session_start();
 3.  define('APP_DIR', realpath('./'));
4.  require(APP_DIR.'/protected/lib/speed.php');

Fatal error: Uncaught Error: Class 'mainController' not found in /home/wwwroot/jubao/en/protected/lib/speed.php:89 Stack trace: #0 /home/wwwroot/jubao/en/index.php(4): require() #1 {main} thrown in /home/wwwroot/jubao/en/protected/lib/speed.php on line 89