Just wanted to have a list so that people who are moving Zen Cart 1.5.5 sites to PHP 7.1 can do these changes by hand before Zen Cart 1.5.6 is released.

Zen Cart 1.5.6 can be found here: https://github.com/zencart/zencart/tree/v156

You can pull a copy of this branch and compare to your local files to find the changes you need.

includes/classes/currencies.php
includes/classes/order.php
includes/functions/functions_taxes.php
includes/classes/categories_ul_generator.php


Linkpoint is no longer operational, but ... if you are somehow still using linkpoint, remember to change $$var references to ${$var} in
includes/modules/payment/linkpoint_api.php