Fixed in CVS:
http://viewcvs.php.net/viewcvs.cgi/php-src/ext/pdo_oci/config.m4.diff?r1=1.14.2.2&r2=1.14.2.3

This patch doesn't completely fix building with pdo-oci on Mac OS X:

checking for oci.h... ./instantclient10_1/sdk/include
configure: error: I'm too dumb to figure out where the libraries are in your instant client install

It does fix the problem with finding the oci.h file, but it then check for a libclntsh.so file, which is not included in the Mac OS X InstantClient ZIP file.
The test -f should use "libclntsh.$SHLIB_SUFFIX_NAME", not "libclntsh.so".

I also had to:
ln -s libclntsh.dylib.10.1 libclntsh.dylib
but I don't think that's related.

Without this last symlink, I was getting this error:

checking Oracle Instant Client version... configure: error: Link from ./instantclient10_1/libclntsh.dylib to libclntsh.dylib.10.1 not found

Finally, after those two errors were fixed, I was getting:

checking for oci.h... ./instantclient10_1/sdk/include
configure: error: Unsupported Oracle version! 

It seems the configure scripts tries to use directory names to guess the version of Oracle when using InstantClient.
For Mac OS X, it should try to guess it using the filename of libclntsh.$SHLIB_SUFFIX_NAME.10.1

Here's a patch tested with Mac OS X 10.4 and InstantClient 10.1 (ZIP files).

*** ext/pdo_oci/config.m4.orig        Wed Feb 15 21:03:13 2006
--- ext/pdo_oci/config.m4       Sat Sep  9 11:27:59 2006
***************
*** 96,111 ****
      else
        AC_MSG_ERROR([I'm too dumb to figure out where the include dir is in your instant client install])
      fi
!     if test -f "$PDO_OCI_IC_PREFIX/lib/oracle/$PDO_OCI_IC_VERS/client/lib/libclntsh.so" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX/lib/oracle/$PDO_OCI_IC_VERS/client/lib"
!     elif test -f "$PDO_OCI_IC_PREFIX/client/lib/libclntsh.so" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX/client/lib"
!     elif test -f "$PDO_OCI_IC_PREFIX/libclntsh.so" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX"
      else
        AC_MSG_ERROR([I'm too dumb to figure out where the libraries are in your instant client install])
      fi
-     PDO_OCI_VERSION="`echo $PDO_OCI_IC_VERS | cut -d. -f1-2`"
    else
      if test -d "$PDO_OCI_DIR/rdbms/public"; then
        PHP_ADD_INCLUDE($PDO_OCI_DIR/rdbms/public)
--- 96,120 ----
      else
        AC_MSG_ERROR([I'm too dumb to figure out where the include dir is in your instant client install])
      fi
!     PDO_OCI_VERSION="`echo $PDO_OCI_IC_VERS | cut -d. -f1-2`"
!     if test -f "$PDO_OCI_IC_PREFIX/lib/oracle/$PDO_OCI_IC_VERS/client/lib/libclntsh.$SHLIB_SUFFIX_NAME" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX/lib/oracle/$PDO_OCI_IC_VERS/client/lib"
!     elif test -f "$PDO_OCI_IC_PREFIX/client/lib/libclntsh.$SHLIB_SUFFIX_NAME" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX/client/lib"
!     elif test -f "$PDO_OCI_IC_PREFIX/libclntsh.$SHLIB_SUFFIX_NAME" ; then
        PDO_OCI_LIB_DIR="$PDO_OCI_IC_PREFIX"
+       if test -f $PDO_OCI_LIB_DIR/libclntsh.$SHLIB_SUFFIX_NAME.10.1; then
+         PDO_OCI_VERSION=10.1
+       elif test -f $PDO_OCI_LIB_DIR/libclntsh.$SHLIB_SUFFIX_NAME.9.0; then
+         PDO_OCI_VERSION=9.0
+       elif test -f $PDO_OCI_LIB_DIR/libclntsh.$SHLIB_SUFFIX_NAME.8.0; then
+         PDO_OCI_VERSION=8.1
+       elif test -f $PDO_OCI_LIB_DIR/libclntsh.$SHLIB_SUFFIX_NAME.1.0; then
+         PDO_OCI_VERSION=8.0
+       fi
      else
        AC_MSG_ERROR([I'm too dumb to figure out where the libraries are in your instant client install])
      fi
    else
      if test -d "$PDO_OCI_DIR/rdbms/public"; then
        PHP_ADD_INCLUDE($PDO_OCI_DIR/rdbms/public)

Using PHP 5.2.0, also on MacOS, configure finishes successfully (it finds the libraries and headers), but it doesn't add the oracle includes to the -I paths for compilation, so compile bails out quickly not finding oci.h. The instantclient files are in /usr/local/oracle/instantclient, with the .h files in /usr/local/oracle/instantclient/sdk/include.

(Even if I copy those files into an include directory that is checked the build fails, but that's because the oracle libs aren't universal and I have an intel mac, which is definitely not PHP's problem.)

I think this workaround should be inserted in the package if possible it's been old story already and it's not in the downloadable package yet. Some students i know are stuck with that problem. Actually the best solution would be a configure option that et the user specify where is the oracle headers such as --with-oci-headers='/path/to/instantclient/headers'.
This kind of problem will occur everytime Oracle will change the directories structure :/

Is this still an issue with any of the actively supported PHP
versions[1]?

[1] <https://www.php.net/supported-versions.php>

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