How to install OCI8 on Ubuntu 16.04 and PHP 7.1
Source: http://www.syahzul.com/2016/04/06/how-to-install-oci8-on-ubuntu-14-04-and-php-5-6/
Install Oracle Instant Client and SDK
Step 1
Download the Oracle Instant Client and SDK from Oracle website. (Need to login in Oracle page)
http://www.oracle.com/technetwork/topics/linuxx86-64soft-092277.html