Fatal error: Uncaught Error: Undefined constant "MB_OVERLOAD_STRING" in /mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/joomla/string/src/phputf8/utf8.php on line 38

Error: Undefined constant "MB_OVERLOAD_STRING" in /mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/joomla/string/src/phputf8/utf8.php on line 38

Call Stack:
    0.0004     358616   1. {main}() /mnt/hosts/h1169705/www/www.graumüller.de/index.php:0
    0.0011     372824   2. require_once('/mnt/hosts/h1169705/www/www.graumüller.de/includes/framework.php') /mnt/hosts/h1169705/www/www.graumüller.de/index.php:40
    0.0040     471360   3. require_once('/mnt/hosts/h1169705/www/www.graumüller.de/libraries/cms.php') /mnt/hosts/h1169705/www/www.graumüller.de/includes/framework.php:18
    0.0043     473528   4. require('/mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/autoload.php') /mnt/hosts/h1169705/www/www.graumüller.de/libraries/cms.php:36
    0.0047     486384   5. ComposerAutoloaderInit205c915b9c7d3e718e7c95793ee67ffe::getLoader() /mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/autoload.php:7
    0.0064     613168   6. composerRequire205c915b9c7d3e718e7c95793ee67ffe($fileIdentifier = '2fb9d6f23c8e8faefc193a4cde0cab4f', $file = '/mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/composer/../joomla/string/src/phputf8/utf8.php') /mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/composer/autoload_real.php:56
    0.0068     618760   7. require('/mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/joomla/string/src/phputf8/utf8.php') /mnt/hosts/h1169705/www/www.graumüller.de/libraries/vendor/composer/autoload_real.php:66