I was hired to install Sentrifugo on a cPanel server where I ran into 500 HTTP error when trying to save site configuration. Other components of the Sentrifugo was working fine but I wasn't able to go pass Configuration Wizard due to this error.

I checked apache error logs, but couldn't find anything related in there. Turns out Sentrifugo runs with APPLICATION_ENV=production. So I enabled development mode by adding following code to .htaccess file,

SetEnv APPLICATION_ENV development

Then tried to save site configuration again and saw the real reason why I couldn't save configuration.

Fatal error: Call to undefined function iconv_strlen() in /home/username/public_html/Zend/Validate/StringLength.php on line 236

I checked phpinfo and found that php was compiled with --with-iconv but module was missing on the server. iconv adds it's own section to phpinfo if it's enabled. So I installed php-iconv with following command.

yum install ea-php56-php-iconv

Client's server was running php 5.6. You must change the php version (e.g. php70, php71) in above command if your PHP version is different.