I'm trying to compile PHP 3.0.15 (happen also with 3.0.14) on a Sun SPARC box running OpenBSD 2.6. I'd like to load PHP as an Apache 1.3.9 DSO module, and when I try to add the DBase support (--with-dbase), this is what I get (it works fine without that option):

$ ./configure --with-dbase --with-apxs=/usr/sbin/apxs --with-config-file-path=/var/www/conf --without-pcre-regex --with-xml --enable-track-vars --with-imap=/usr/src/local/imap-4.7a/c-client

[... some stuff removed ...]

(cd dbase; gmake libdbf.a)
gmake[1]: Entering directory `/usr/src/local/php-3.0.15/dbase'
gcc -I. -I. -g -O2 -DDEV_RANDOM=/dev/arandom -DMOD_SSL=204105 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -O2   -c dbf_head.c -o dbf_head.o
gcc -I. -I. -g -O2 -DDEV_RANDOM=/dev/arandom -DMOD_SSL=204105 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -O2   -c dbf_rec.c -o dbf_rec.o
gcc -I. -I. -g -O2 -DDEV_RANDOM=/dev/arandom -DMOD_SSL=204105 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -O2   -c dbf_misc.c -o dbf_misc.o
gcc -I. -I. -g -O2 -DDEV_RANDOM=/dev/arandom -DMOD_SSL=204105 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -O2   -c dbf_ndx.c -o dbf_ndx.o
rm -f libdbf.a
ar crv libdbf.a dbf_head.o dbf_rec.o dbf_misc.o dbf_ndx.o
a - dbf_head.o
a - dbf_rec.o
a - dbf_misc.o
a - dbf_ndx.o
ranlib libdbf.a
gmake[1]: Leaving directory `/usr/src/local/php-3.0.15/dbase'
ar rc libmodphp3-so.a language-parser.tab.o language-scanner.o main.o php3_hash.o operators.o variables.o token_cache.o stack.o internal_functions.o snprintf.o php3_sprintf.o alloc.o list.o highlight.o debugger.o configuration-parser.tab.o configuration-scanner.o request_info.o safe_mode.o fopen-wrappers.o constants.o php3_realpath.o alloca.o php_compat.o  functions/adabasd.o functions/aspell.o functions/apache.o functions/fhttpd.o functions/basic_functions.o functions/crypt.o functions/datetime.o functions/db.o functions/dbase.o functions/dir.o functions/dl.o functions/dns.o functions/exec.o functions/file.o functions/filepro.o functions/filestat.o functions/formatted_print.o functions/fsock.o functions/gd.o functions/head.o functions/html.o functions/image.o functions/imap.o functions/php3_mcal.o functions/php_ftp.o functions/ftp.o functions/imsp.o functions/link.o functions/mail.o functions/math.o functions/iptc.o functions/md5.o functions/microtime.o functions/mime.o functions/msql.o functions/mysql.o functions/oracle.o functions/oci8.o functions/pack.o functions/pageinfo.o functions/pgsql.o functions/magick.o functions/post.o functions/rand.o functions/reg.o functions/solid.o functions/soundex.o functions/string.o functions/syslog.o functions/type.o functions/uniqid.o functions/sybase.o functions/sybase-ct.o functions/url.o functions/base64.o functions/info.o functions/bcmath.o functions/number.o functions/xml.o functions/unified_odbc.o functions/ldap.o functions/browscap.o functions/velocis.o functions/gdttf.o functions/gdcache.o functions/zlib.o functions/COM.o functions/ifx.o functions/pdf.o functions/cpdf.o functions/hw.o functions/hg_comm.o functions/dlist.o functions/fdf.o functions/wddx.o functions/wddx_a.o functions/snmp.o functions/var.o functions/interbase.o functions/quot_print.o functions/cyr_convert.o functions/sysvsem.o functions/dav.o functions/sysvshm.o functions/gettext.o functions/php3_mckcrypt.o functions/yp.o functions/dba.o functions/dba_gdbm.o functions/dba_dbm.o functions/dba_ndbm.o functions/dba_cdb.o functions/mcrypt.o functions/dba_db2.o functions/mhash.o functions/pcre.o functions/posix.o functions/parsedate.o functions/lcg.o functions/recode.o  dbase/dbf_head.o dbase/dbf_rec.o dbase/dbf_misc.o dbase/dbf_ndx.o
ranlib libmodphp3-so.a
/usr/sbin/apxs -c -o libphp3.so  -I. -I.  ./mod_php3.c libmodphp3-so.a -L/usr/local/lib  /usr/src/local/imap-4.7a/c-client/lib/c-client.a                              -L./dbase -ldbf  -lm  -lresolv  
gcc -DDEV_RANDOM=/dev/arandom -DMOD_SSL=204105 -DEAPI -DUSE_EXPAT -I../lib/expat-lite -fPIC -DSHARED_MODULE -I/usr/lib/apache/include -I. -I.  -c ./mod_php3.c
ld -Bforcearchive -Bshareable -o libphp3.so ./mod_php3.o libmodphp3-so.a -L/usr/local/lib /usr/src/local/imap-4.7a/c-client/lib/c-client.a -L./dbase -ldbf -lm -lresolv 
dbf_head.c:20: Definition of symbol `_get_dbf_head' (multiply defined)
dbf_head.c:68: Definition of symbol `_free_dbf_head' (multiply defined)
dbf_head.c:118: Definition of symbol `_get_dbf_field' (multiply defined)
dbf_head.c:88: Definition of symbol `_put_dbf_head' (multiply defined)
dbf_head.c:202: Definition of symbol `_get_dbf_f_fmt' (multiply defined)
dbf_head.c:150: Definition of symbol `_put_dbf_field' (multiply defined)
dbf_head.c:185: Definition of symbol `_put_dbf_info' (multiply defined)
dbf_head.c:223: Definition of symbol `_dbf_open' (multiply defined)
dbf_head.c:249: Definition of symbol `_dbf_head_info' (multiply defined)
dbf_rec.c:19: Definition of symbol `_get_dbf_record' (multiply defined)
dbf_rec.c:43: Definition of symbol `_get_piece' (multiply defined)
dbf_rec.c:57: Definition of symbol `_put_dbf_record' (multiply defined)
dbf_rec.c:75: Definition of symbol `_put_piece' (multiply defined)
dbf_rec.c:86: Definition of symbol `_del_dbf_record' (multiply defined)
dbf_rec.c:101: Definition of symbol `_pack_dbf' (multiply defined)
dbf_rec.c:134: Definition of symbol `_get_field_val' (multiply defined)
dbf_rec.c:147: Definition of symbol `_put_field_val' (multiply defined)
dbf_rec.c:155: Definition of symbol `_out_rec' (multiply defined)
dbf_rec.c:172: Definition of symbol `_is_valid_rec' (multiply defined)
dbf_rec.c:180: Definition of symbol `_dbf_get_next' (multiply defined)
dbf_misc.c:21: Definition of symbol `_get_long' (multiply defined)
dbf_misc.c:30: Definition of symbol `_put_long' (multiply defined)
dbf_misc.c:45: Definition of symbol `_get_short' (multiply defined)
dbf_misc.c:53: Definition of symbol `_put_short' (multiply defined)
dbf_misc.c:57: Definition of symbol `_get_double' (multiply defined)
dbf_misc.c:74: Definition of symbol `_put_double' (multiply defined)
dbf_misc.c:89: Definition of symbol `_copy_fill' (multiply defined)
dbf_misc.c:99: Definition of symbol `_copy_crimp' (multiply defined)
dbf_misc.c:110: Definition of symbol `_db_set_date' (multiply defined)
dbf_misc.c:124: Definition of symbol `_db_date_year' (multiply defined)
dbf_misc.c:133: Definition of symbol `_db_date_month' (multiply defined)
dbf_misc.c:142: Definition of symbol `_db_date_day' (multiply defined)
dbf_misc.c:153: Definition of symbol `_db_cur_date' (multiply defined)
dbf_ndx.c:17: Definition of symbol `_ndx_get_header' (multiply defined)
dbf_ndx.c:157: Definition of symbol `_ndx_get_first_rec' (multiply defined)
dbf_ndx.c:170: Definition of symbol `_ndx_get_next_rec' (multiply defined)
dbf_head.c:20: Definition of symbol `_get_dbf_head' (multiply defined)
dbf_head.c:68: Definition of symbol `_free_dbf_head' (multiply defined)
dbf_head.c:118: Definition of symbol `_get_dbf_field' (multiply defined)
dbf_head.c:88: Definition of symbol `_put_dbf_head' (multiply defined)
dbf_head.c:202: Definition of symbol `_get_dbf_f_fmt' (multiply defined)
dbf_head.c:150: Definition of symbol `_put_dbf_field' (multiply defined)
dbf_head.c:185: Definition of symbol `_put_dbf_info' (multiply defined)
dbf_head.c:223: Definition of symbol `_dbf_open' (multiply defined)
dbf_head.c:249: Definition of symbol `_dbf_head_info' (multiply defined)
dbf_rec.c:19: Definition of symbol `_get_dbf_record' (multiply defined)
dbf_rec.c:43: Definition of symbol `_get_piece' (multiply defined)
dbf_rec.c:57: Definition of symbol `_put_dbf_record' (multiply defined)
dbf_rec.c:75: Definition of symbol `_put_piece' (multiply defined)
dbf_rec.c:86: Definition of symbol `_del_dbf_record' (multiply defined)
dbf_rec.c:101: Definition of symbol `_pack_dbf' (multiply defined)
dbf_rec.c:134: Definition of symbol `_get_field_val' (multiply defined)
dbf_rec.c:147: Definition of symbol `_put_field_val' (multiply defined)
dbf_rec.c:155: Definition of symbol `_out_rec' (multiply defined)
dbf_rec.c:172: Definition of symbol `_is_valid_rec' (multiply defined)
dbf_rec.c:180: Definition of symbol `_dbf_get_next' (multiply defined)
dbf_misc.c:21: Definition of symbol `_get_long' (multiply defined)
dbf_misc.c:30: Definition of symbol `_put_long' (multiply defined)
dbf_misc.c:45: Definition of symbol `_get_short' (multiply defined)
dbf_misc.c:53: Definition of symbol `_put_short' (multiply defined)
dbf_misc.c:57: Definition of symbol `_get_double' (multiply defined)
dbf_misc.c:74: Definition of symbol `_put_double' (multiply defined)
dbf_misc.c:89: Definition of symbol `_copy_fill' (multiply defined)
dbf_misc.c:99: Definition of symbol `_copy_crimp' (multiply defined)
dbf_misc.c:110: Definition of symbol `_db_set_date' (multiply defined)
dbf_misc.c:124: Definition of symbol `_db_date_year' (multiply defined)
dbf_misc.c:133: Definition of symbol `_db_date_month' (multiply defined)
dbf_misc.c:142: Definition of symbol `_db_date_day' (multiply defined)
dbf_misc.c:153: Definition of symbol `_db_cur_date' (multiply defined)
dbf_ndx.c:17: Definition of symbol `_ndx_get_header' (multiply defined)
dbf_ndx.c:157: Definition of symbol `_ndx_get_first_rec' (multiply defined)
dbf_ndx.c:170: Definition of symbol `_ndx_get_next_rec' (multiply defined)
apxs:Break: Command failed with rc=65536
gmake: *** [libphp3.so] Error 1
$

Note that I had a problem quite similar on that platform with the Perl regex support, and it was cleared by simply adding the flag "--without-pcre-regex".