So I installed Omeka Classic using XAMPP server. I encountered this error:
Zend_Session_Exception
Zend_Session::start() - C:\xampp\htdocs\omeka\application\libraries\Zend\Db\Table\Rowset\Abstract.php(Line:368): Error #8192 Return type of Zend_Db_Table_Rowset_Abstract::offsetUnset($offset) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice
Zend_Session_Exception: Zend_Session::start() - C:\xampp\htdocs\omeka\application\libraries\Zend\Db\Table\Rowset\Abstract.php(Line:368): Error #8192 Return type of Zend_Db_Table_Rowset_Abstract::offsetUnset($offset) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in C:\xampp\htdocs\omeka\application\libraries\Zend\Session.php:509
Stack trace:
#0 C:\xampp\htdocs\omeka\application\libraries\Zend\Session\Namespace.php(143): Zend_Session::start(true)
#1 C:\xampp\htdocs\omeka\application\libraries\Zend\Auth\Storage\Session.php(86): Zend_Session_Namespace->__construct('Zend_Auth')
#2 C:\xampp\htdocs\omeka\application\libraries\Zend\Auth.php(91): Zend_Auth_Storage_Session->__construct()
#3 C:\xampp\htdocs\omeka\application\libraries\Zend\Auth.php(141): Zend_Auth->getStorage()
#4 C:\xampp\htdocs\omeka\application\libraries\Omeka\Application\Resource\Currentuser.php(42): Zend_Auth->hasIdentity()
#5 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(695): Omeka_Application_Resource_Currentuser->init()
#6 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(641): Zend_Application_Bootstrap_BootstrapAbstract->_executeResource('Currentuser')
#7 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(598): Zend_Application_Bootstrap_BootstrapAbstract->_bootstrap('Currentuser')
#8 C:\xampp\htdocs\omeka\application\libraries\Omeka\Application\Resource\Helpers.php(116): Zend_Application_Bootstrap_BootstrapAbstract->bootstrap('Currentuser')
#9 C:\xampp\htdocs\omeka\application\libraries\Omeka\Application\Resource\Helpers.php(27): Omeka_Application_Resource_Helpers->_initAclHelper()
#10 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(695): Omeka_Application_Resource_Helpers->init()
#11 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(641): Zend_Application_Bootstrap_BootstrapAbstract->_executeResource('Helpers')
#12 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(598): Zend_Application_Bootstrap_BootstrapAbstract->_bootstrap('Helpers')
#13 C:\xampp\htdocs\omeka\application\libraries\Omeka\Application\Resource\Frontcontroller.php(63): Zend_Application_Bootstrap_BootstrapAbstract->bootstrap('Helpers')
#14 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(695): Omeka_Application_Resource_Frontcontroller->init()
#15 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(638): Zend_Application_Bootstrap_BootstrapAbstract->_executeResource('frontcontroller')
#16 C:\xampp\htdocs\omeka\application\libraries\Zend\Application\Bootstrap\BootstrapAbstract.php(598): Zend_Application_Bootstrap_BootstrapAbstract->_bootstrap('frontcontroller')
#17 C:\xampp\htdocs\omeka\application\libraries\Zend\Application.php(373): Zend_Application_Bootstrap_BootstrapAbstract->bootstrap(NULL)
#18 C:\xampp\htdocs\omeka\application\libraries\Omeka\Application.php(49): Zend_Application->bootstrap()
#19 C:\xampp\htdocs\omeka\admin\index.php(28): Omeka_Application->initialize()
#20 {main}