Your PHP Version is 5.6.20-1+deb.sury.org~trusty+
1, but always_populate_raw_post_data = 0. $HTTP_RAW_POST_DATA is deprecated from PHP 5.6 onwards and will be removed in PHP 7.0. This will stop the installer from running. Please open your php.ini file and set always_populate_raw_post_data to -1. If you need more help please call your hosting provider.