Thanks Matt,
below is exactly what I used, and it works:
./configure i386-redhat-linux
--with-freetype-dir=/usr --with-gettext --with-openssl
--with-pspell --with-regex=system --with-config-file-path=/etc --with-xml
--enable-bcmath --enable-ftp --enable-magic-quotes --enable-safe-mode
--enable-sockets --with-mysql=/usr --with-pgsql=shared --enable-ucd-snmp-hack
--with-unixODBC=shared --enable-dbx --enable-mcal
--with-sybase=/opt/sybase-11.9.2 --enable-pic --with-png-dir=/usr --with-zlib
--with-gd --enable-gd-native-ttf --with-jpeg-dir=/usr --with-png
--with-apxs=/usr/sbin/apxs
but, if I change the above configure line of '--with-sybase=/opt/sybase-11.9.2' with '--with-sybase-ct=/opt/sybase-11.9.2'
and it does not work.
I thought the libs from sybase would work with the option of --with-sybase-ct=/opt/sybase-11.9.2