Po zmianie PHP z 7.4 na 8.1 , strona nie działa i otrzymuje takie błędy:


Fatal error: Uncaught Error: Undefined constant "MB_OVERLOAD_STRING" in /home/mgoks/ftp/bibnowa/libraries/vendor/joomla/string/src/phputf8/utf8.php:38 Stack trace: #0 /home/mgoks/ftp/bibnowa/libraries/vendor/composer/autoload_real.php(66): require() #1 /home/mgoks/ftp/bibnowa/libraries/vendor/composer/autoload_real.php(56): composerRequire205c915b9c7d3e718e7c95793ee67ffe('2 fb9d6f23c8e8fa...', '/home/mgoks/ftp...') #2 /home/mgoks/ftp/bibnowa/libraries/vendor/autoload.php(7): ComposerAutoloaderInit205c915b9c7d3e718e7c95793ee6 7ffe::getLoader() #3 /home/mgoks/ftp/bibnowa/libraries/cms.php(36): require('/home/mgoks/ftp...') #4 /home/mgoks/ftp/bibnowa/includes/framework.php(18): require_once('/home/mgoks/ftp...') #5 /home/mgoks/ftp/bibnowa/index.php(40): require_once('/home/mgoks/ftp...') #6 {main} thrown in /home/mgoks/ftp/bibnowa/libraries/vendor/joomla/string/src/phputf8/utf8.php on line 38

Czy mógłby mi ktoś pomóc?