Frontpage not working

[Sun Feb 09 20:59:50.920007 2020] [:error] [pid 27830] [client 192.168.1.104:47936] PHP Notice: Undefined index: username in /var/www/html/toolkits/website_code/php/management/get_templates_for_user.php on line 79, referer: /toolkits/management.php?register [Sun Feb 09 20:59:50.920058 2020] [:error] [pid 27830] [client 192.168.1.104:47936] PHP Notice: Undefined index: username in /var/www/html/toolkits/website_code/php/management/get_templates_for_user.php on line 126, referer: /toolkits/management.php?register [Sun Feb 09 20:59:50.920107 2020] [:error] [pid 27830] [client 192.168.1.104:47936] PHP Notice: Undefined index: login_id in /var/www/html/toolkits/website_code/php/management/get_templates_for_user.php on line 126, referer: /toolkits/management.php?register [Sun Feb 09 20:59:50.922509 2020] [:error] [pid 27830] [client 192.168.1.104:47936] PHP Notice: Undefined variable: row_templates in /var/www/html/toolkits/website_code/php/management/get_templates_for_user.php on line 127, referer: /toolkits/management.php?register [Sun Feb 09 20:59:50.922572 2020] [:error] [pid 27830] [client 192.168.1.104:47936] PHP Notice: Undefined index: template_id in /var/www/html/toolkits/website_code/php/management/get_templates_for_user.php on line 127, referer: toolkits/management.php?register [Sun Feb 09 21:00:04.848085 2020] [:error] [pid 27831] [client 192.168.1.104:47940] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in /var/www/html/toolkits/website_code/php/xwdInspector.php:47\nStack trace:\n#0 /var/www/html/toolkits/website_code/php/xwdInspector.php(87): XerteXWDInspector->isValidXml('<?xml version="...')\n#1 /var/www/html/toolkits/website_code/php/management/templates.php(41): XerteXWDInspector->loadTemplateXML('/var/www/html/t...')\n#2 {main}\n thrown in /var/www/html/toolkits/website_code/php/xwdInspector.php on line 47, referer: toolkits/management.php?register [Sun Feb 09 21:00:07.978411 2020] [:error] [pid 27832] [client 192.168.1.104:47942] PHP Notice: Use of undefined constant MANAGEMENT_TUTORIAL_TEXT - assumed 'MANAGEMENT_TUTORIAL_TEXT' in /var/www/html/toolkits/website_code/php/management/site.php on line 70, referer: /toolkits/management.php?register [Sun Feb 09 21:00:07.982117 2020] [:error] [pid 27832] [client 192.168.1.104:47942] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_file() in /var/www/html/toolkits/website_code/php/language_library.php:38\nStack trace:\n#0 /var/www/html/toolkits/website_code/php/management/management_library.php(217): getLanguages()\n#1 /var/www/html/toolkits/website_code/php/management/site.php(262): language_details(false)\n#2 {main}\n thrown in /var/www/html/toolkits/website_code/php/language_library.php on line 38, referer: /toolkits/management.php?register [Sun Feb 09 21:00:16.109642 2020] [:error] [pid 27832] [client 192.168.1.104:47942] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:00:50.654547 2020] [:error] [pid 27833] [client 192.168.1.104:47952] Failed to load language file for Xerte - en-GB/editor/js/vendor/jquery-1.9.1.min.js, referer: /toolkits/management.php?register [Sun Feb 09 21:00:51.162722 2020] [:error] [pid 27833] [client 192.168.1.104:47952] PHP Notice: Use of undefined constant MANAGEMENT_TUTORIAL_TEXT - assumed 'MANAGEMENT_TUTORIAL_TEXT' in /var/www/html/toolkits/website_code/php/management/site.php on line 70, referer: /toolkits/management.php?register [Sun Feb 09 21:00:51.171296 2020] [:error] [pid 27833] [client 192.168.1.104:47952] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_file() in /var/www/html/toolkits/website_code/php/language_library.php:38\nStack trace:\n#0 /var/www/html/toolkits/website_code/php/management/management_library.php(217): getLanguages()\n#1 /var/www/html/toolkits/website_code/php/management/site.php(262): language_details(false)\n#2 {main}\n thrown in /var/www/html/toolkits/website_code/php/language_library.php on line 38, referer: /toolkits/management.php?register [Sun Feb 09 21:03:15.644043 2020] [:error] [pid 27830] [client 192.168.1.104:47974] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:06:18.522639 2020] [:error] [pid 27833] [client 192.168.1.104:48020] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:06:43.395599 2020] [:error] [pid 27834] [client 192.168.1.104:48026] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:07:03.866152 2020] [:error] [pid 28520] [client 192.168.1.104:48032] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:07:16.198173 2020] [:error] [pid 27830] [client 192.168.1.104:48034] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:07:32.258761 2020] [:error] [pid 27831] [client 192.168.1.104:48038] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:07:44.597647 2020] [:error] [pid 27832] [client 192.168.1.104:48040] PHP Warning: Invalid argument supplied for foreach() in /var/www/html/toolkits/website_code/php/management/management_library.php on line 89, referer: /toolkits/management.php?register [Sun Feb 09 21:08:46.657487 2020] [:error] [pid 27834] [client 192.168.1.104:48064] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_file() in /var/www/html/toolkits/website_code/php/language_library.php:38\nStack trace:\n#0 /var/www/html/toolkits/website_code/php/language_library.php(96): getLanguages()\n#1 /var/www/html/toolkits/website_code/php/login_library.php(270): display_language_selectionform('')\n#2 /var/www/html/toolkits/website_code/php/login_library.php(382): login_form(Array, Object(stdClass))\n#3 /var/www/html/toolkits/index.php(50): login_processing()\n#4 {main}\n thrown in /var/www/html/toolkits/website_code/php/language_library.php on line 38

sudo apt install php-xml

service apache2 restart