The user profile update code in net-mgmt/zabbix4-frontend requires the php filter module which is part of the security/phpXY-filter port/package. Installing this port/package resolves the issue. It should be added as a dependency of zabbix4-frontend, and possibly older ports of Zabbix if it affects them as well. I havn't tested it on them. I upgraded to Zabbix 4 and wanted to use the dark theme and was unable to update my user profile.

Steps to reproduce.

1. Login to Zabbix
2. Click the user profile icon (Looks like a silhouette head and shoulders)
3. Click update
4. Get the below stack trace and profile is not updated.

Fatal error: Uncaught Error: Call to undefined function filter_var() in /usr/local/www/zabbix4/include/classes/validators/CEmailValidator.php:35 Stack trace: #0 /usr/local/www/zabbix4/include/classes/api/services/CUser.php(673): CEmailValidator->validate('jdmulloy@gmail....') #1 /usr/local/www/zabbix4/include/classes/api/services/CUser.php(450): CUser->validateMediaRecipients(Array, Array) #2 /usr/local/www/zabbix4/include/classes/api/services/CUser.php(316): CUser->validateUpdate(Array, Array) #3 /usr/local/www/zabbix4/include/classes/api/clients/CLocalApiClient.php(123): CUser->update(Array) #4 /usr/local/www/zabbix4/include/classes/api/wrappers/CFrontendApiWrapper.php(97): CLocalApiClient->callMethod('user', 'update', Array, '5fc4e351b8a5582...') #5 /usr/local/www/zabbix4/include/classes/api/wrappers/CApiWrapper.php(94): CFrontendApiWrapper->callClientMethod('update', Array) #6 /usr/local/www/zabbix4/include/classes/api/wrappers/CFrontendApiWrapper.php(63): CApiWrapper->callMethod('update', Array) #7 /usr/local/www/zab in /usr/local/www/zabbix4/include/classes/validators/CEmailValidator.php on line 35