Changed my version of php to 7 and the site wouldn't load at all.
CS-Cart 4.3.9 is officially support PHP 7.0. However, it also depends on 3rd party add-ond and how they prepared for usage with PHP 7.0. Did you check compatibility of your extensions?
The following probably has nothing to do with the php stumble but it's is repeated the most.
[02-Dec-2016 16:44:24 Australia/Sydney] PHP Notice: Undefined index: category_ids in /home/jameshou/public_html/app/functions/fn.catalog.php on line 6932
Below was the last error recorded before some 'Stack Trace' records started....
[02-Dec-2016 06:05:11 UTC] PHP Fatal error: Uncaught Error: Class 'mysqli' not found in /home/jameshou/public_html/app/Tygh/Backend/Database/Mysqli.php:40
Below was the last error recorded before some 'Stack Trace' records started....
[02-Dec-2016 06:05:11 UTC] PHP Fatal error: Uncaught Error: Class 'mysqli' not found in /home/jameshou/public_html/app/Tygh/Backend/Database/Mysqli.php:40
Most likely this one because mysqli was not installed with the PHP7 version.
.When I moved from 5.6 I took a few steps, cleared out cache, set cache to database and gave the server tech who did it a list of things that needed to be installed in the new php7 configuration so that cs-cart would run. First had to update easyapache before php7. It stumbled a bit at first because he didn't get everything in php setup correctly, but eventually it worked and then I was able to switch cache to apcu and things have been fine. A weird issue where googlepage speed was reporting gzip not compressing html, even though nothing changed in the htaccess file, but that was fixed by adding rules to the pre_main_global.conf file.