This article outlines the details of OCI client support in the PHP buildpack.
The binary builder supports building the oci8 and pdo_oci extensions for PHP versions 5.5, 5.6, and 7.0. While it is capable of building these extensions, it does not include the Oracle libraries and SDK required for the build. These components are not provided by the binary builder due to licensing restrictions, and the builder does not automatically download them because they are behind an Oracle paywall. To build the extensions, you must manually download and provide these dependencies to the builder.
List of artifacts to download and the build process has been described here https://github.com/cloudfoundry/binary-builder/blob/main/PHP-Oracle.md