Fatal error: Uncaught Error: Class 'Zend\Validator\AbstractValidator' not found in /home/app/htdocs/lidia/vendor/zendframework/zend-validator/src/Isbn.php:12 Stack trace: #0 {main} thrown in /home/app/htdocs/lidia/vendor/zendframework/zend-validator/src/Isbn.php on line 12