Fatal error: Uncaught TypeError: strcmp() expects parameter 1 to be string, object given in /var/www/module/StudyCourse/src/StudyCourse/Mapper/Db/StudyCourseDbMapper.php:417 Stack trace: #0 /var/www/module/StudyCourse/src/StudyCourse/Mapper/Db/StudyCourseDbMapper.php(417): strcmp(Object(SelectionCriterion\Entity\FieldOfStudy), Object(SelectionCriterion\Entity\FieldOfStudy)) #1 [internal function]: StudyCourse\Mapper\Db\StudyCourseDbMapper->StudyCourse\Mapper\Db\{closure}(Object(StudyCourse\Entity\StudyCourse), Object(StudyCourse\Entity\StudyCourse)) #2 /var/www/module/StudyCourse/src/StudyCourse/Mapper/Db/StudyCourseDbMapper.php(418): usort(Array, Object(Closure)) #3 /var/www/module/StudyCourse/src/StudyCourse/Service/StudyCourseService.php(124): StudyCourse\Mapper\Db\StudyCourseDbMapper->fetchAllNames() #4 /var/www/module/Application/src/Application/Controller/InfoController.php(116): StudyCourse\Service\StudyCourseService->fetchAllNames() #5 /var/www/vendor/zendframework/zend-mvc/src/Controller/AbstractActionController. in /var/www/module/StudyCourse/src/StudyCourse/Mapper/Db/StudyCourseDbMapper.php on line 417