File access fails in external lib called from extension

I have an external library (C++, .so shared lib) that uses <fcntl.h> functions (open, etc) to access local disk resources, to create a data repository. I have written a standalone KDE client that affirms that the library is functioning correctly. When I try to use a class from that library in a PHP-C++ extension however, the class is usable, but the file io fails. Is this a permissioning issue? (Apache/Php not allowing calls to disk access?) Or am I missing something? Should a C/C++ extension still be able to access system/file IO? Cheers, Andrew