What is new in PHP 7.1 ?

Answer 1

Let me google that for you :)
http://www.letmegooglethat.com/?q=What+is+new+in+PHP+7.1

Answer 2

One thing for sure (I recompiled PHP7 on my phone / Termux to run a webserver): native MySQL drivers. This is a major break from previous database methods.

For what it's worth, I used MariaDB from Google Play and PHP + native MySQL was fine.

Answer 3

These questions are more appropriate to google yourself.