So I am in the process of setting up a new server for VuFind and documented the steps I took to get PHP to compile with PDO-OCI. I do remember that I did struggle with it a bit the very first time I did it:
So here are the steps to make it work:
1. Download PHP :)
2. Download the Basic.zip and SDK.zip from the Oracle Instant Client web site
3. Unzip the 2 zip files in the same directory
4. Move the instantclient directory to somewhere on your server (/usr/local/lib is generally the place to put it)
5. Create a symbolic link from the libclntsh.so.11.1 (or whatever version you have) to libclntsh.so as well as the same for libocci.so….
6. Configure PHP with the option '--with-pdo-oci=instantclient,/usr/local/lib/instantclient,220.127.116.11'
You may need to change the configure option to match the path that you have installed the instantclient to as well as the version that you downloaded.
This has worked for me on both 32 and 64 bit machines.