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($controller_nametrue)) {
80.              err("Err: Controller '$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