I configured PHP as follows:
configure --enable-track-vars --with-apache=../apache_1.3.12 --with-oci8=$ORACLE_HOME
I then edited the config.h file and set the line
#define HAVE_OCI8 0
to
#define HAVE_OCI8 1
I then had to edit the Makefile in order to add a few additional paths for the include files.
Added
-I/usr/local/oracle/product/805/rdbms/demo -I/usr/local/oracle/product/805/plsql/public
-I/usr/local/oracle/product/805/network/public
to the INCLUDE line
and also added:
-L/usr/local/oracle/product/805/lib
to the LDFLAGS line of the Makefile
Then I ran make & make install, which reported no errors.
At this point I went on to build apache.