Please update accordingly or better yet provide a legacy branch/release as it's frustrating to assume that this will work based on the requirements provided but then come to find out it doesn't. I discovered this running PHP 5.3.3 which I realize is old but a lot of companies move slow and as a developer sometimes your hands are tied in these situations.
Currently the dependencies section of the README is: PHP 5.0 or later
This commit makes the minimum 5.4 as you implemented the use of the JsonSerializable interface: https://github.com/avadev/AvaTax-Calc-REST-PHP/commit/14bb73c1c177c485e9d7398c648e10bc3377e306
Please update accordingly or better yet provide a legacy branch/release as it's frustrating to assume that this will work based on the requirements provided but then come to find out it doesn't. I discovered this running PHP 5.3.3 which I realize is old but a lot of companies move slow and as a developer sometimes your hands are tied in these situations.
Thanks!