Simple configure line:

./configure --disable-all --enable-cli --with-oci8=$ORACLE_HOME

Even though backtrace ends up deep into oracle libraries, I belive this to be PHP bug since both PHP 4.2.2 and sqlplus work without any problems on the same box and same database (8.1.7).

#0  0x4007ea9a in zero () at eval.c:41
#1  0xbfffb494 in ?? ()
#2  0x4021e397 in kgupasgaatt ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#3  0x4021f675 in kgupaicon ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#4  0x4021e2b7 in kgupascdrv ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#5  0x4021d5f6 in kgupacon ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#6  0x401eac4d in kgup_process_connect ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#7  0x4018f460 in kpushInit ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#8  0x404c7895 in kpummpin ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#9  0x4018f5a6 in kpupin ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#10 0x401bc037 in OCIInitialize ()
   from /home/oracle8/ora01/app/oracle/product/8.1.7/lib/libclntsh.so.8.0
#11 0x0805b6e0 in zm_startup_oci (type=1, module_number=2)
    at /data/src/PHP_4_3/ext/oci8/oci8.c:489
#12 0x080d1b3b in zend_startup_module (module=0x810d940)
    at /data/src/PHP_4_3/Zend/zend_API.c:1005
#13 0x080adf67 in php_startup_extensions (ptr=0x8115890, count=2)
    at /data/src/PHP_4_3/main/main.c:1049
#14 0x080e778e in php_startup_internal_extensions ()
    at main/internal_functions_cli.c:53
#15 0x080ae325 in php_module_startup (sf=0x8115800, additional_modules=0x0,
    num_additional_modules=0) at /data/src/PHP_4_3/main/main.c:1215
#16 0x080e6ce8 in main (argc=2, argv=0xbffff9e4)
    at /data/src/PHP_4_3/sapi/cli/php_cli.c:481
#17 0x40672306 in __libc_start_main (main=0x80e6be4 <main>, argc=2,