TimeTrex hasn't been tested on PHP v7.1 yet, so until that is done the installer will fail.
Since v7.1 isn't in any stable Linux releases yet, and our automated installer uses v7.0, supporting bleeding edge PHP versions it not a high priority, but we will likely get around to testing it in early 2018.
As stated - NOT a Linux server! Windows install only allows MySQL - and we have PostgreSQL due to ERP (which TimeTrex does support - though not really identified anywhere). Server already running Apache and PHP and there is NO instructions on how to manual install or specifications needed for Windows server. Your Windows install is lacking customization for existing servers.
PHP 7.1 not stable? Php 7.1.0 came out stable back in Dec 2016 and really the specifications (via early version) has been out since June 9 2016 (over a year ago) and 7.2 is about to be released (Beta 3 released just yesterday). Why not stable? On PHP its been stable for more than half a year? 7.2 is considered NOT stable and been out for 2 months now.
Sounds like a typical open source software - we get to it some time in a year or two or sooner if some one want to pay for it now.
Looks like they removed functions that was depreciated several versions ago - which by now should have been changed for anyone using 7.0 anyway. They added more functions and a few changes needed to be version 7.1 compatible.
You should up date to version 7.1 but vector to be compatible to version 7.2 so in a year or so when you get to updating it you have the compatibility for 7.2 when that is stable later this year or early next year.
It was not my server but said that is what was updated to.