When comiling PHP with apxs (DSO support), the CFLAGS line in pcrelib/Makefile doesn't import CFLAGS_SHLIB from the top-level Makefile, so compiler flags for creating a shared library don't get activated. This causes a compilation failure at link time because libpcre.a isn't created sharable.  

        ranlib libmodphp3-so.a
        /dfs/opt/apache/bin/apxs -c -o libphp3.so  -I. -I.  ./mod_php3.c libmodphp3-so.a -L/usr/local/lib                          -L/dfs/opt/informix/lib -L/dfs/opt/informix/lib/esql -lixsql -lixasf -lixgen -lixos -lixgls -lnsl_s -lV3 -lcl -lsec /dfs/opt/informix/lib/esql/checkapi.o -lixglx     pcrelib/libpcre.a -lm   -Lpcrelib -lpcre
cc -DHPUX10 -Aa -D_HPUX_SOURCE -DUSE_HSREGEX -DUSE_EXPAT -I../lib/expat-lite -Ae +DAportable -O +z -DSHARED_MODULE -I/dfs/opt/apache/include -I. -I.  -c ./mod_php3.c
ld -b -o libphp3.so ./mod_php3.o libmodphp3-so.a -L/usr/local/lib -L/dfs/opt/informix/lib -L/dfs/opt/informix/lib/esql -lixsql -lixasf -lixgen -lixos -lixgls -lnsl_s -lV3 -lcl -lsec /dfs/opt/informix/lib/esql/checkapi.o -lixglx pcrelib/libpcre.a -lm -Lpcrelib -lpcre 
ld: Invalid loader fixup for symbol "$0000000D".
apxs:Break: Command failed with rc=65536
*** Error exit code 1

I had to add "+z -DSHARED_MODULE" to the CFLAGS line in pcrelib/Makefile to link correctly.

My configure line was:
./configure --with-informix \
            --with-config-file-path=/etc/opt/apache \
            --with-apxs=/dfs/opt/apache/bin/apxs \
            --with-xml