After completing Site registration form et click on next button.

Fatal error: The web server did not finish its request
Contact website owner with current url and info on what you did, and owner will be able to debug the issue further (by enabling 'display_errors' in php.ini).

$ tail -f /var/log/apache2/error.log
Cannot redeclare class ezfsfilehandler in /ezpublish_legacy/kernel/classes/ezdatatype.php on line 1306