I have compiled php4.0.5 with oracle(oci7) as DSO without problems, but enabling php4 together with mod_perl dumps core (segfault) on starting apache.
PHP4.0.5 works, if I either disable mod_perl or compile php4.05 without oracle support.
If I compile PHP3.0.18 with oracle and enable it together with mod_perl (both DSO) everything works well.

I use Apache/1.3.14, mod_perl-1.24_01 (DSO)

php configuration line:
./configure --prefix=/opt/apache --with-apxs=/opt/apache/bin/apxs --x-includes=/usr/openwin/include --x-libraries=/usr/openwin --enable-force-cgi-redirect --enable-discard-path --enable-calendar --with-db=/usr --with-ndbm=/usr --enable-ftp --enable-gd-native-ttf --with-gd=/usr/local --with-jpeg-dir=/usr/local --with-xpm-dir=/usr/openwin --with-ttf=/usr/local --with-oracle=/opt/oracle --enable-trans-sid --without-mysql --disable-xml --with-gnu-ld

gdb backtrace:
bash-2.01$ gdb /opt/apache/bin/httpd /core 
GNU gdb 4.17
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "sparc-sun-solaris2.6"...
Core was generated by `/opt/apache/bin/httpd'.
Program terminated with signal 11, Segmentation Fault.
Reading symbols from /usr/lib/libsocket.so.1...done.
Reading symbols from /usr/lib/libnsl.so.1...done.
Reading symbols from /usr/lib/libdl.so.1...done.
Reading symbols from /usr/lib/libc.so.1...done.
Reading symbols from /usr/lib/libmp.so.2...done.
Reading symbols from /usr/platform/SUNW,Ultra-4/lib/libc_psr.so.1...done.
Reading symbols from /usr/lib/libX11.so.4...done.
Reading symbols from /usr/lib/libXext.so.0...done.
Reading symbols from /opt/apache/libexec/mod_vhost_alias.so...done.
Reading symbols from /opt/apache/libexec/mod_env.so...done.
Reading symbols from /opt/apache/libexec/mod_log_config.so...done.
Reading symbols from /opt/apache/libexec/mod_mime.so...done.
Reading symbols from /opt/apache/libexec/mod_negotiation.so...done.
Reading symbols from /opt/apache/libexec/mod_status.so...done.
Reading symbols from /opt/apache/libexec/mod_info.so...done.
Reading symbols from /opt/apache/libexec/mod_include.so...done.
Reading symbols from /opt/apache/libexec/mod_autoindex.so...done.
Reading symbols from /opt/apache/libexec/mod_dir.so...done.
Reading symbols from /opt/apache/libexec/mod_cgi.so...done.
Reading symbols from /opt/apache/libexec/mod_asis.so...done.
Reading symbols from /opt/apache/libexec/mod_imap.so...done.
Reading symbols from /opt/apache/libexec/mod_actions.so...done.
Reading symbols from /opt/apache/libexec/mod_userdir.so...done.
Reading symbols from /opt/apache/libexec/mod_alias.so...done.
Reading symbols from /opt/apache/libexec/mod_rewrite.so...done.
Reading symbols from /opt/apache/libexec/mod_access.so...done.
Reading symbols from /opt/apache/libexec/mod_auth.so...done.
Reading symbols from /opt/apache/libexec/libproxy.so...done.
Reading symbols from /opt/apache/libexec/mod_expires.so...done.
Reading symbols from /opt/apache/libexec/mod_unique_id.so...done.
Reading symbols from /opt/apache/libexec/mod_setenvif.so...done.
Reading symbols from /opt/apache/libexec/libperl.so...done.
Reading symbols from /usr/lib/libm.so.1...done.
Reading symbols from /opt/apache/libexec/libphp4.so...done.
Reading symbols from /usr/lib/libpam.so.1...done.
Reading symbols from /opt/oracle/lib/libclntsh.so.1.0...done.
Reading symbols from /usr/lib/libposix4.so.1...done.
Reading symbols from /usr/lib/libz.so.1.0.2...done.
Reading symbols from /usr/openwin/lib/libXpm.so.4.7...done.
Reading symbols from /usr/lib/libresolv.so.2...done.
Reading symbols from /usr/lib/libaio.so.1...done.
#0  0xef5c5998 in _smalloc ()
(gdb) bt
#0  0xef5c5998 in _smalloc ()
#1  0xef5c59e0 in malloc ()
#2  0xef04d538 in Perl_savepvn ()
#3  0xef0262bc in Perl_gv_init ()
#4  0xef026050 in Perl_gv_fetchfile ()
#5  0xef022ed4 in open_script ()
#6  0xef020608 in perl_parse ()
#7  0xef0090a0 in perl_startup ()
#8  0xef008ba8 in perl_module_init ()
#9  0x232f4 in ap_init_modules ()
#10 0x31464 in standalone_main ()
#11 0x32180 in main ()
(gdb)