session_start(): Cannot start session when headers already sent

Call Stack

1. in Session.php line 106
2. at Error::appError(2, 'session_start(): Can...', '/mnt/yk/cms/thinkphp...', 106, ['config' => ['id' => '', 'var_session_id' => '', 'prefix' => 'think', ...], 'isDoStart' => true])
3. at session_start() in Session.php line 106
4. at Session::init() in Session.php line 120
5. at Session::boot() in Session.php line 164
6. at Session::get('admin') in Auth.php line 170
7. at Auth->isLogin() in Backend.php line 144
8. at Backend->_initialize() in Index.php line 24
9. at Index->_initialize() in Controller.php line 59
10. at Controller->__construct(object(Request))
11. at ReflectionClass->newInstanceArgs([object(Request)]) in App.php line 359
12. at App::invokeClass('app\admin\controller...') in Loader.php line 479
13. at Loader::controller('index', 'controller', false, 'Error') in App.php line 580
14. at App::module(['', null, null], ['app_host' => '', 'app_debug' => true, 'app_trace' => false, ...], true) in App.php line 456
15. at App::exec(['type' => 'module', 'module' => ['', null, null]], ['app_host' => '', 'app_debug' => true, 'app_trace' => false, ...]) in App.php line 139
16. at App::run() in start.php line 19
17. at require('/mnt/yk/cms/thinkphp...') in index.php line 31