To choose the php version that suits you best please follow these instructions:
(Usually for Prestashop 1.7, the PHP version 7 is mandatory. While for 1.6 it is advised. While for Wordpress or others CMS the 7.0 might be better)
You have go in User, in the top panel:
Then you have to go in Account manager - Domain setup. Then click on your domain name:
Then you have to click on the PHP Version Selector button on the top right panel:
After that you'll be led to a menu where you can choose your PHP version:
