u.masotti wrote:

>> ./configure --with-interbase=shared,/path/to/firebird
>
> Here problems arose:
> checking for InterBase support... yes, shared
> checking for isc_detach_database in -lfbclient... no
> checking for isc_detach_database in -lgds... no
> checking for isc_detach_database in -lib_util... no
> configure: error: libgds, libib_util or libfbclient not found! Check
> config.log for more information.
>
> Firebird is dispersed in some directories (there is nothing in
> /opt/firebird)

That's probably the way debian/ubuntu package is created.

> configure:3944: checking for isc_detach_database in -lfbclient
> configure:3979: gcc -o conftest -g -O2
> -Wl,-rpath,/usr/lib/firebird/2.0/lib -L/usr/lib/firebird/2.0/lib
> conftest.c -lfbclient >&5
> /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/libfbclient.so:
> undefined reference to `_Unwind_RaiseException'

FBClient refers to _Unwind_RaiseException symbol (most probably a
function), which the linker cannot find. It looks to me as a C++ error
handling function, so it isn't strange that C compiler cannot find it.
Changing gcc to g++ in configure script might work, although I'm not
sure this is the right thing to do.

> Any hints?

Obviously there are some changes in Firebird package that make it
incompatible with vanilla PHP sources. You should either:

a) reinstall Firebird using the .tar.gz from official FB website
b) contact the Ubuntu/Debian package maintainer and ask them
c) try to figure it out on your own

I'd go for a) myself, but it's your choice.

Good luck,

--
Milan Babuskov
http://www.guacosoft.com