Steps to reproduce:

1. Make sure when you don't have php filter extension installed.
2. Login to Zabbix
3. Click the user profile icon (Looks like a silhouette head and shoulders)
4. Click update
5. Get the below stack trace and profile is not updated.

Result:

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

Reported by: Joseph Mulloy
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233005

IMHO needs a patch on `CFrontendSetup.php` and in the documentation.

https://www.zabbix.com/documentation/current/manual/installation/requirements
https://github.com/zabbix/zabbix/blob/trunk/frontends/php/include/classes/setup/CFrontendSetup.php