The OCI8 extension for Oracle Database can be linked with Oracle's client libraries called “Oracle Instant Client”.

1. Download the Oracle 10gR2 Instant Client “basic” and “sdk” zip files.
2. Unzip the “basic” package and rename the directory as lib/instantclient
3. Unzip the “sdk” package and rename the directory as include/instantclient
4. Build with the --with-oci8 option
5. Move the generated php_oci8.dll to the extensions directory, edit php.ini and set “extension_dir” to that path, and enable the extension with “extension=php_oci8.dll”

Instant Client is free and has a permissive license.

Download: Oracle Instant Client

License: “OTN Development and Distribution License Agreement for Instant Client” (Viewable as a Javascript popup prior to downloading).

The php_oci8.dll released with PHP 5.1 and 5.2 used Oracle Instant Client 10gR2 aka 10.2.