I have gone through the whole process of downloading Oracle instant client, SDK, etc. in a Ubuntu Server 17.04. Then converted rpm packages to deb with alien, installed, set
As you still will have the same problem with php cli with the above solution, it would be better to add a new file /etc/ld.so.conf.d/oracle.conf with this content:
/usr/lib/oracle/12.2/client64/lib
Then run
sudo ldconfig
This way it works for apache and php cli and you do not need to change /etc/apache2/envvars