The answer to my own question: WHM --> Software --> EasyApache
My current configuration was shown at the top and was selected (radio button). I edited that and selected Exhaustive List of Options. I was able to select several items including mysqli, mbstring, json, mcrypt, XML, date, openssl, sockets, soap, xmlwriter ... hard to believe so many of those were missing many were my next problem I just had not yet discovered.
EasyApache recompiled apache/php for me and restarted apache automagically. MySQLi was now included along with the other elements I selected.
To further configure PHP - I had to use phpinfo to find the php.ini file it is loading and edit that as root (sudo). There is a facility located in
WHM --> Service Configuration --> PHP Configuration Editor
that can be used instead but it is unlikely all options will be available using this page. Also: see note below: I had to manually edit php.ini to configure the new stuff.
I'd like to also point out that there are additional sections that should have been added to the php.ini file but were not. There should be a section to configure mysqli (separate from mysql [native driver]), mbstring, soap etc. These are not present in the php.ini file on my server after running EasyApache to update PHP. I had to edit the php.ini file and add the sections for them and restart apache. Just FYI
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…